I was on the last floor of the catacombs, quite a hard game for me as it took awhile to get there and I was looking forward to victory. But now my saves won't work.

Anyone else had this happen?

Screenshot included.

I do have the steam version also, maybe I could copy my save games to there?

Make sure you're running the game as administrator.

If the problem is copying the file out of the save, that could be a problem.
Check the number of files in the saved game folder (before going to the Dark Forest or Verdistis there should be 22), and specifically that inv.b0 exists.

Each save is a separate subfolder in the '..\Divine Divinity\savegames' folder.
Under Vista/7, depending on how the user accounts are set up, if you install the game to the default Program Files path, Windows can create separate savegame folders for each user, and then map that folder to the game's savegame folder (so it will just see the saves for the relevant user).
C:\Users\ %account name% \AppData\Local\VirtualStore\Program Files\Divine Divinity\savegames


However, if the error is copying the file to the dynamic folder, then simply deleting all the files in the '..\Divine Divinity\Dynamic' folder should fix the it. To be safe you could move those files to a new subfolder, or something, until you check that your saves work.
This folder is used as a cache for the game. Files are created / copied there from the save game folder when you load, and written / copied from that folder when you save a game. The files will be re-created as required the next time you start Divinity. If there was a corrupt file in that folder, deleting the files should fix the problem.

Since multiple saves are effected the problem is most likely with the file in the dynamic folder, but check the saves first. One person with the disk version of the game had a crash in Windows some time after they quit the game, and upon reboot windows deleted all the inv.b2 files in their saves, likely assuming they were corrupt because they were zero bytes (though being zero bytes it was easy to replace the files). If something similar happened with your saves, the inv.b0 file in the dynamic folder would be your best shot at replacing that missing file in your latest save.

I had 21 saves, all my latest saves were missing the inv.b0 file, the earlier ones were not.

The dynamic folder did not contain a inv.b0 file which is strange since the game was loading and working yesterday. I did not modify the files or folders or delete anything at any time.

I might try the steam version when I can be bothered, as the catacombs would be a chore to have to do again for a while. I hear the game is much more pleasant after the test of fire, but I will wait a little while.

I don't know what happened to the files, but unfortunately the Steam version isn't going to be able to handle the missing file, either.

You could replace the inv.b0 file in your latest save with that from your most recent working save. However, this file keeps track of things you have equipped and things in your inventory, so that would change. Any missing quest items or teleporter stones, etc, could be replaced (Lost Items - guide and directory of inventory files). If you do not have any backup equipment in a chest or on the ground at your home base, you could re-create what you lost (or as best you can remember, anyway) using DAD's item editor.

Alternately, you could go back to your most recent working save, and use the item editor to give a weapon a large damage and stat boost, so you can easily and quickly re-clear the catacombs up to where you were, then switch back to a regular weapon to continue.

I might try that tomorrow, thanks. I would have to put the item's stats back as the difficulty is what makes it good. The lowest level, in the tomb was getting pretty crazy lol. Zombies and exploding spiders...