My problem started when I updated to Windows XP SP 2. When I realised that a lot of people had NWN problems with SP2, I used the Windows XP roll-back feature to undo the update, and it worked fine once after that. However, since then, I haven't been able to get it working.
The first time I ran NWN after installing SP2, it asked me something like "do you want to allow this program through". I never had troubles after that. I don't think that the crashes I had were specifically caused by SP2 (i had some before that anyway).
Morrus, it seems to me like most PW servers have already patched to 1.64, even those using CEP, like Higher Ground (which also runs PoA). I don't think it would cause too much trouble. But of course, it's your call... And I'm biased because I miss the server.
I still think the best path is to update NWN to 1.64, then update to CEP 1.5 final (tomorrow is the scheduled release date) and then update to PrC 2.2b (scheduled soon). This way the server would feel "new and improved". Of course this is only my opinion