Mine never reset ever when I first got it, then it started doing it frequently for a little while, then much less often. Maybe once or twice a week now. I've decided to live with it.
It will occasionally do it when I use ShadowPlan 3.0,
http://www.codejedi.com, depending on the size of the file I have open.
It seems to happen nearly 50% of the time when I do a bluetooth hotsync.
Sometimes when it's already syncing and I plug it in to be recharged.
...that's about it. Generally, when I'm making unusually heavy demands of the processor, and/or putting it in a position where an application might write past the end of a buffer.
Generally, this comes under the category of not going nuts when you load third-party apps onto it. Allocate a few days, maybe a week, to fully test out each one. If you aren't doing anything like that and still having problems, it might be time to talk about workmanship issues & warranty exchanges.
Hope this helps.