For me, my nano2g just hangs randomly sometimes. It looks like there are builds that cause more panics than others, but so far I haven't been able to find any relation between the changes from each build and the hangs. It looks like it happens more often when there the playlist files are of different formats - Rockbox seems to hang when changing codecs sometimes, although that doesn't happen for a while now, so it should be fixed (perhaps, it was fixed unintentionally by the buflib changes).
The errors always happen at different points in memory and they aren't very frequent (some months ago, the situation was way worse - panics every 5 min), so I don't bother reporting each of them - even because some happen with the screen turned off. I just reboot the iPod and restart playing.