In my 80Gb 5.5 a lot of weird things happen, including yours. But a hard reset and often visit to the OF will normalize everything.
About the noises, I haven't ever played music using the OF, only a couple of videos, so I can't compare.
A quick list of weird things I note. Some of them have been discussed here.
> The battery expiring icon when turn on.
Fix: Hard Reset, going to the OF with the hold on switch, and then reset again. Seems to do something that fix whatever.
> Having a Theme, a font, a splash, etc. Sometimes will bot with the original layout, the tiny font and the plain black background.
Fix: Hard Reset
> Harsh and terrific noises when changing manually a song, having the crossfader enabled. Wont play more after that.
Fix: Stop and play again
> Total hang of everything but the music. No key operation, no screen update.
Fix: Hard Reset
> Auto turn-on silently in the nigh, starting to play, draining the battery. (Even if you set the initial screen to menu, and wake up alarm off)
Fix:Let it rest with the hold on switch enabled. When it decides to startup, will do in OF, so in a couple of minutes will turn off again, saving the batteries.
> Slow USB transfer
Fix: Always do the USB in Apple mode.
> Error message about the file access: Sometimes, when browsing the files while playing and the song ends to play another, you will get some system error.
Fix: Nothing more happens. The play will continue, and you can continue browsing.