If you are using the pro version of Avira System Speedup, its 'Automatic cleaning & speed optimization' feature is probably causing the conflict. With the free version I'm not sure if it does anything in real time, but it may remain running in the background.
Try disabling real time / automatic features, or exit out of the program (there should be an option not to have it run on Windows startup) and just run it when needed.
If you are also using Avira's anti-virus, you should be able to
add an exception for the game/editor install path and/or the game's My Documents folder. Alternately, disable real time scanning in Avira.
