I know very little but I will try to help with what I think are common problems.
First make sure you are running PC in its own window (not tab)
I have mine pointed to - "
https://www.mturk.com/mturk/welcome?pandacrazy=on&usenewsite=yes"
Running other things too fast will cause PRE's, such as running HF with too many results and too fast of a scan delay.
PC cycle time is shown at the topish left - just left of the PRE number, if it is high try reseting the cycle timer in PC using the "reset timer" radio button.
The number of panda's you have running should not cause PRE's but the more you run the longer it takes to go through the list sand you might not catch things.
What do you have running now?