I am having this issue with PS:T that started not too far into the game. Whenever I click to the inventory screen or map screen or character stats screen or any screen that is not the main real time screen, it only stays there for about 5 seconds then automatically goes back to the real time screen. The same thing happens when I try the right-click quick item screen and also when I try to pick up an item. Also the dialogue scrolls to the end of the conversation and I can't go back and find out what was said. And also I can't use the mouse to scroll the mouse pointer, I have to use the arrow keys. I am using the GOG version with no mods or fixes and using WinXP with nVidia GeForce 6100. I hope this is fixable because this is getting to be almost unplayable with these various glitches.

I'm not sure what could fix it, but you should probably take a look at the mod sticky and install some of the bug fixes at minimum. That could alleviate some of the issues.

This topic may also help. At least, that's what got my game to work. I was using a slightly newer card than you, though.

Thanks for the link. I notice the performance is severely reduced when i switched to software rendering. But running in hardware acceleration introduce another weird glitch. Hopefully this one can solve the performance issue.