Troubleshooting KindleDX Int'l cannot connect anymore after 2.5.8

[ArdjanB]

A few days ago, I discovered I recieved an update: the orientation was set on 'auto', instead of my usual 'portrait'. Then I saw I have now 2.5.8.

But now, I can't get connected to the wireless anymore!

If I switch on wirelesse, it gets switched off less than a minute later. The signal quality was always good where I tried it (large city).
I tried to switch off/on, I tried a reset: nothing.
I downloaded 2.5.7, put it in the root directory, but the moment I opened the menu in the settings screen, the line 'update...' briefly flashes black, and is then grey again. When I connect to my PC, the bin-file is gone. The same with 2.5.8 bin file.

I already sent a ticket to Amazon, but recieved 'try a reset' first. I am reluctant to call, because of the telephone costs from Austria, Europe...

As a last resort, I tried to reset to factory, and that went well: everything is gone (I made a backup of music & documents first ), but I can't register it: the wireless doesn't work (long enough) to enter email & pw...

Anyone here got an idea?

Thanks in advance,
Ardjan