My D2 is acting weirdly. Maybe battery is shot??

[sps7]

I have the original D2, purchased in March 2008. It's worked fine 'til very
recently. About 1 week ago, I noticed I had trouble trying to shut it off.
Pushing the on-off switch seemed to work but then the D2 would start up again. It was difficult to shut off but I finally succeeded. Now things have worsened. I can't even use it because it keeps restarting over and over. Does this mean the battery is shot (which means I have to mail it in to Cowon to put in a new battery)? Or is something else wrong with my D2??

Just before this problem started, I had a corrupt music flac file on the D2. Only the first third of the file would play and then the D2 would just suddenly turn black and shut off due to some failure. I transferred all the flac files from my 16 GB card, deleted the bad flac file, and then transferred back to the 16 GB card all the flac music files. This seemed to work but then, at some point, the recent weird shutdown and start problems began. I don't know if the older bad-flac-file was the cause of the newer shutdown-start problems.

What could be wrong? What's the solution?

[Firmware: 2.59]

My computer OS is MEPIS 11, a Linux distro.

Thanks