NV+ won't boot, displaying "Welcome to readynas wolrd!"

[hannovk]

Hi!
Since 5 years I am happily using a NV+ at home, usuall runnig 24/7. After replacing the power supply (in my device the power suppy never lived longer than 2 years...) I booted the NV+ for test purpose and it sucessfully started up so that I could acess the shares and the configurationpage without problems.
So I shut it down again to transport it to it's normal place, and since that moment it refuses to work at all.

When I press the power button at the front, the blue light of the power button pulsates one time, the HDD-lamps flicker the usuall short blink at startup and the display greets me with "Welcome to the Readynas world!". And then the boot process stops completely. The OS is not loaded, the sound of my four discs spinnig up does not come, nothing. The message stays for ever, pressing power button 5 sec to shutdown does not work. The only way to shut down system is unpluggin the power cord.

That's what I have tried so far:
- Booting without disks: same result
- Try the memory-test by pressing power button 25 Sekons: nothing happens, LEDs do not flash as they should

Any suggestions what I should do? Thanks for your help.
Hanno