Hi ipy,
Two, maybe three times in the last 13 months, this has happened to me also. Each time it was near the end of the track but not at the very end. And, each time I was able to press the 'next track' button on the remote and continue on. At the time I did not try to replay the paused tracks, but I have on occasions before and since and they are fine. So, it is not a ripping/compression issue.
I am using 6.2.1/FW15, ripping using EAC/FLAC and my modded SB2 is connected wirelessly with an average signal strength of approx 80%. I suspect that it may be caused by a momentary interruption to the router signal or an infrequent glitch at the PC or SB2 but don't really know. As it only happens about twice a year I haven't worried about tracing the cause.