I disagree. I think PAF does have a memory leak bug. I also have experienced a great slowdown when I try to enter too much data at once.
I did what you suggested (scandisk, defrag) and it did take a long time (I read instead of drinking coffee) and when it finished, I restarted.
It took longer to reach the slowdown, but it still happened. I did notice however, that it happens sooner if I am running background programs such as RealJukebox to listen to music.
Moreover, I found that I could only enter about 25 names before noticing the slowdown originally, then it increased to about 75 after the defrag. and not playing music. The way I enter data, after entering it, I click on the source button and paste a memorized citation. I do this one to three times per individual plus on Family Sources when entering a spouse. I think the problem stems from opening and closing so many windows in quick succession in order to fully document my data.
Even though only two people in this forum have complained about it, maybe that's because most people aren't entering such high volumes of data manually in a single sitting.
The PAF technicians should really check into this.