It's because sometimes FPHG outputs a corrupt hand history and for some reason HEM HUD locks up when it sees it (not sure why it happens more for SNGs than for cash). This in turn then causes the Party client to lock up, whilst giving the false impression that FPHG has caused the crash (ie: if HEM HUD freezes it causes the message queue of the table to stall as well).
Trying to tweak the FPHG settings won't really have any effect as if FPHG finds something that looks like a HH file (but is actaully a corrupted copy that's being moved around in memory) then it will effect both active and passive modes similarly.
In the last version of FPHG I tried hard to make as few of these corrupted hands as possible get output, but really there isn't much more I can do and a certain amount of these has to be expected. To solve the HEM HUD lock-up problem you really need to get onto the HEM people and ask that they fix their parsing / error detection routines so that it doesn't lock up when these corrupt files are encountered.