All I can sugest is that you restart your system and make sure nothing unusal is running in the background, you can check exactly what is running by hitting ctrl+alt+delete and clicking on task manager.

Basicly what I am hinting at is that heavy memory or cpu use may be causing a problem with pSX

It may even be a virus that your machine has picked up that may be effecting pSX (Ad-ware and or Root Kits may not be detected by normal anti virus software)