ah ... might be a clash yes. I have heard of side effects from a screensaver before. Not for some time though. Check to see exactly what your screensaver does & your system settings. I have my computer (HDD & monitor) set to never sleep & screensaver only runs if I manually trigger it to. I suspect your HDD might be slowed down perhaps when your screensaver comes on. Well ... let's hope that's the reason anyway.

I only sleep my computer when I manually set it to. I need to do this due to rendering I need to do for work. If my HDD or cpu went to sleep whilst rendering then it would cancel it or permanently slow it down or cause some type of problem, possibly even a crash.