This is the answer I got today from iRiver:
Considering all of the information you have provided for us regarding this issue, we have decided that this is a hardware issue and your unit needs to be sent in for a repair service.
I'm pretty sure that this is a software problem, as at least frostschutz was able to reproduce. May please someone else try to reproduce it, to convince this people to fix the problem?
@frostschutz: I'm currently very busy at work, but will check your file ASAP.