I have also been having this issue, and in addition sometimes when skipping forward or back the song will not play and just hangs on 0.00. The only way to get any song to play then is to go back into the file browser and select that or another song. Very frustrating.
One interesting thing to note, is that my friend is having a similar issue on his ipod which does NOT have rockbox installed, but just using the apple firmware.
This makes me wonder if the problem might be from initializing the ipod with a new version of itunes which may have a bug in it. I recently had my ipod replaced by apple, so I initialized it with the newest version of itunes before loading rockbox on it. Is it possible that the problem some people are having might arise from the initialization and not from the rockbox firmware?
Hopefully someone with more technical knowledge of what actually happens when an ipod is initialized can shed some light on this...