I'm having that problem too...and from time to time I also get pauses of a few seconds between tracks with the W-symbol on. During that time there's no error-messages on the serial-output or any strange noises from the HDs, so I also believe something's wrong with caching.
And it happens more often with Hijack... see this thread
(If you wonder about my last message there: after those 2 days it happened again... but the behaviour really seems to change with every new installation of the empeg-software...somehow...)