Hi tesshan
Some of the older Cool-ER firmwares can be a bit temperamental - if a particular book makes it crash, the reader will sometimes continually try to load that same book on start. I keep my books on an SD card, so if it does get into this sort of problem I can just take the SD card out and it won't crash when loading the book since it's not there.
As cyberman suggested before - a complete reflash with the latest firmware should solve the problem.
It shouldn't matter what the PC says, the Cool-ER only really wants a connection for power reasons.
As the Cool reader site has gone down I've uploaded a copy of the latest firmware
here.