In Antwort auf:

One other note or two. If you are detecting DC power, that will both change the speed of the serial ports down to 4800 and will also not allow flash upgrades.

Well, I read that somewhere and tried to set the speed to 4800, but this brought up weird characters in hyperterminal... it looked like word salad...
So I assume that there is some line in my config.ini saying "serial=115200" or something like this. I assume I read this once and thought that setting this would be a good idea...

As far as I know, the empeg kernel would skip the upgrade process completely if DC power is detected, so this is probably not the cause for the problem.

But thank anyway for your suggestion