Hello. This strange, corruption sort of bug is keeping me from playing almost all of the game. I wont be able to enjoy the story until I can find a fix.

So I made a single player character (an evil Barbarian) with a strength of 18 and a thing for greataxes!
Over the time of three play sessions (using saves naturally) I completed the prologue, got a silver shard and walked over to the world menu.

I tried to transition to the path to Neverwinter, but then my game crashed to a screen that says "Log in rejected Strref error!" This screen then asks me to pick from one of the pre generated characters to continue.
I refuse to throw away my character.

I looked up strref and it seems to be a dev error code for "Corruption Detected" or even "hacked statistics detected."

I am running no mods and have not edited the game files. Therefore, the game must be getting corrupted somehow.

I use Windows 10, a GTX980 card.

I think you're referring to NWN2 rather than NWN1. First of all try to load an earlier save and check whether the error will continue to occur. When you start a new module in NWN2 (every new chapter is treated as a separate module) the game imports certain values from the previous one. This includes characters and their inventory. Maybe the characters were were imported with errors. In this case loading an earlier save may solve the problem. If it doesn't help, you probably have corrupted game files. Verifying them through GOG Galaxy or redownloading and reinstalling the game should allow you to continue without any issues. :)

If you're talking about the error message visible on the screenshot, then this is probably a question for the developers. :) I'm not a C++ programmer, so I can't provide you any details. It's possible to fix your saves however. Check the solution in this post: https://gamefaqs.gamespot.com/boards/946862-neverwinter-nights-2-storm-of-zehir/47935776. Be sure to use the appropriate files. These that are used by the main campaign are different from these used by the expansion packs.

Ok, this is what happened when I followed that 10 year old advice.
I replaced the ".Z" file of the corrupted character's save with a ".Z" file of a brand new character.
It booted!
However, my character is now in a soft lock situation.
The starting town is in two states at the same time. (In has the grey dwarves invading, but most of the key characters are standing in their end of prologue positions.)
The world map will not give me the option to travel toward Neverwinter without talking to the Step Dad first.
Problem is: The Step Dad is not in his position in this state! He is not around becasue we have not "dealt with the invastion yet" due to replacing the damaged ".Z" file.
Help?

I guess you're out of luck. This method doesn't work in every location. Anomalies can occur because you're mixing fresh location files with existing saves. In some locations you can normalize the situation by launching scripts that push the game forward. This is probably not one of them. If you don't have any other saves, probably you will have to start from the beginning. You can always try to contact support, but this is probably a typical gameplay bug, so I'm not sure if they'll be able to help you: https://support.gog.com/hc/en-us.

Guess I will start playing a different RPG for now.

I just hope someone with a way to prevent corrupting in the first place see this open question some day.

Issue still not resolved. Starting the game again would likly still result in random corruption like the first time.

Will monitor this thread from time to time.

I'm thinking that with the "log in" error, you might try uninstalling and DLing and installing the game files only with the "download offline backup game installers" option.