I am on my 4th iRiver iFP-899 since November 2004.
It is now February 2005.
#1 just locked up one day while on the tread mill.
The display was frozen and the machine did not respond to a pushed button. I reset(taking out the battery) but this did not help. I sent it back, iRiver sent me a new one.
#2 and #3 have basically the same problem. They each worked fine for ~20hours of use then started to have white noise and static problems. The static and white noise could be heard when not playing music. The output amps just went bad I think.
#4 Is OK with ~3 hours on it.

I don't know why they go bad but they do.