Hrm. There is nothing in the log file indicating these Problems. But seeing your "Mobile" Setup, I might want to suggest that this could be caused by a thermic problem on your card, e.g. it is getting too hot and therefore starts making problems. You could try the following:
- Steam Library, right-click "realms of Arcania"
- Choose Tab "Properties", click "Browse local files...."
- go to directory "schick_data/Data"
- Open file "globalsettings.xml" with a text editor
- find "-1"
- replace "-1" by e.g. "25"
- save the file
- start the game

This limits the number of frames displayed to a maximum of 25 per Second. This shouldn't bother your game experience, but it should reduce the juice it needs from the graphics card. Find a value to your liking, but I wouldn't go further than 40, after all, you're playing an oldschool rpg and not some shooter .

I'll recheck the framelimiter effect. Be aware that it only takes effect after restarting the game