WOW!!!!
I fixed the evil imp bug!
Is this an error in the GOG version of the game? Has anyone actually finished the GOG version???

Interesting.. I've not used any of those spells you were talking about, so I have no clue what caused the problem. I'd be interested to know if anybody else completed the GOG version without issue. I guess I'll have to find a hex editor.
Tell me if you are able to finally finish the game.

Well, Zaknandrix transported me to the magical world, but when I reach Antx, he is hostile and will not speak to me.
So, I am still unable to finish the quest.
Hex editing the save file should be listed as part of the quest.
The game is still broken.
I wish I had just played the CD-Rom version.

DOH!
:(

I wasn't sure there would be a fix for this problem . . .+1 for extra effort . . .=)
Could you post the name and a link to the hex editor you used? If you could also post a screen shot of the hex editor displaying the lines you edited . . . that might be helpful to others as well . . .

Okay, here is more info on how to fix the Evil Imps Bug in Divine Divinity.
This fix will prevent Zaknadrix and Antx from becoming hostile and attacking instead of speaking with the hero.
This time I'll attach pictures as requested.
A simple hex editor is required. I use the free version of Hex Edit found here:
http://www.hexedit.com/
For this explanation, I'm using the '.' to represent an hex value of '00'
In the Divine Divinity 'savegames' folder, locate a save just before confronting Zaknadrix.
Use Hex Edit to open the data.000 file
Search for the text 'Zanadrix' (notice there is no 'k' in the name)
Ignore the first match and look for the second and third matches which look like this:
ASCII = "Zanadrix59.....Zanadrix.K"
HEX = "5A 61 6E 61 64 72 69 78 35 39 00 09 00 00 00 5A 61 6E 61 64 72 69 78 00 4B"
Overwrite the hex value for both Z's with 00 so the string now looks like:
ASCII = ".anadrix59......anadrix.K"
HEX = "00 61 6E 61 64 72 69 78 35 39 00 09 00 00 00 00 61 6E 61 64 72 69 78 00 4B" Now go back to the top of the document and start another search for "Antx47"
Ignore the first match and look for the second and third matches which look like this:
ASCII = "Antx47.....Antx.K"
HEX = "41 6E 74 78 34 37 00 05 00 00 00 41 6E 74 78 00 4B"
Overwrite the hex value for both A's with 00 so the string now looks like:
ASCII = ".ntx47......ntx.K"
HEX = "00 6E 74 78 34 37 00 05 00 00 00 00 6E 74 78 00 4B"
Save the data.000 file
Run Divine Divinity, load the modified save and play!
Now both Zaknadrix and Antx are friendly and will speak to the hero allowing for the completion of the Council of 7 quest for the Imp.
Enjoy!
-PitBrat

Thanks for the images and info . . .=)

Though it doesn't affect any quests, I noticed that the two Orcs at the start of the Desert level are hostile when they should be friendly; Garth and Drox.
The Garth has a few lines of dialogue, but Drox also sells items. Here is a fix for when the Orcs are hostile and refuse to speak or sell items.
Fixing the Orcs, Garth and Drox :
Again, load of the hex editor.
Open the data.000 from your savegame folder.
Search for the text 'Orc drox186"
Ignore the first match and look for the second one which looks like this:
ASCII = "Orc drox186.....Orc drox"
HEX = "4F 72 63 20 64 72 6F 78 31 38 36 00 09 00 00 00 4F 72 63 20 64 72 6F 78"
Overwrite the hex value for the O's in both Orcs with 00 so the string now looks like:
ASCII = ".rc drox186......rc drox"
HEX = "00 72 63 20 64 72 6F 78 31 38 36 00 09 00 00 00 00 72 63 20 64 72 6F 78"
Now go back to the top of the document.
Start a search for 'Orc garth185"
Ignore the first match and look for the second one which looks like this:
ASCII = "Orc garth185.....Orc garth"
HEX = "4F 72 63 20 67 61 72 74 68 31 38 35 00 0A 00 00 00 4F 72 63 20 67 61 72 74 68"
Overwrite the hex value for the O's in both Orcs with 00 so the string now looks like:
ASCII = ".rc garth185......rc garth"
HEX = "00 72 63 20 67 61 72 74 68 31 38 35 00 0A 00 00 00 00 72 63 20 67 61 72 74 68"
Save the data.000 file
Run Divine Divinity, load the modified save and play!

I discovered another related bug.
The Dragon Patriarch becomes hostile after exiting the conversation and won't teach you the ghost spell.
Here is the fix to prevent the Dragon Patriarch from becoming hostile after exiting the conversation.
Open the data.000 file from the savegame folder in an hex editor.
Search for the text 'patriarch153"
Ignore the first match and look for the second one which looks like this:
ASCII = "Patriarch153.....Patriarch"
HEX = "50 61 74 72 69 61 72 63 68 31 35 33 00 0A 00 00 00 50 61 74 72 69 61 72 63 68"
Overwrite the hex value for the P's with 00 so the string now looks like:
ASCII = ".atriarch153......atriarch"
HEX = "00 61 74 72 69 61 72 63 68 31 35 33 00 0A 00 00 00 00 61 74 72 69 61 72 63 68"
Save the data.000 file
Now the Dragon Patriarch no longer becomes hostile upon exiting the conversation.

okay, I'm hoping for a patch that eventually fixes this issue, because I don't feel like hacking the game endlessly to complete it. :(

I don't believe we will be seeing another patch for this game. The one just released took several months and was probably the last for this old game.
I don't know of any other cases like these two either so it's doesn't seem to be a common problem. I would suggest both of you open help tickets with GOG support, maybe post your system specs for comparison as it may be a specific video card, driver or computer brand that you have in common.
I don't have any suggestions beyond installing on a completely different computer and see if you get the same results, if so, might be a corrupted setup.exe and re-downloading might be a solution. . . =)

Between this forum and the Larian forum, it appears that quite a few people are encountering this issue. I contacted Larian and that basically had this to say:
"Unfortunately I don't think we will release a new patch, at least, a new patch is not planned at the moment, but that can always change in the future."
I'm still waiting to hear from someone who has played the GOG version of this game all the way through without encountering this bug.
Despite it's niggles, Divine Divinity is an awesome game and well worth the effort to finish. Though at this point I feel like "Hex Edit data.000" should be a quest objective.
Now when should we expect Divinity III ???

Divinity II is the next release since Beyond Divinity was not considered to be 2 . . .=)
Edit:
I have never encountered this bug either in the unpatched or the newly patched GOG version.

I have Divinity 2 - Ego Draconis.. It's actually quite good. But looks like they still haven't ironed out issues with quicksaving, as when you quicksave the game, the quickload, it doesn't load from the last quicksave, but the quicksave prior to that one.. So the quicksave works, but quickload is essentially useless. :(
No game-breaking bugs in it that I've found so far, though. :)