Sorry, tried to load the old 5-3-x config to version 5.4.x, but no luck, the AP's cycle through all the boot and config stages, so no luck there.
Tried a downgrade from 5.5.x to 5.4 x today, the config was completely gone, had to enter IP manually to get web management on the controller again. Then a downgrade to my old 5.3.x-version, lost config/IP again, set new IP, and restored my old 5.3.x-config, and soon all the AP's started to downgrade and got back online. (between these stages I used an ACL on the switch to prevent the AP's access to the controller, in case they would start loading an incorrect config out of control - a good safety mesure). All my AP's are routed, none are directly connected with VLAN, so an ACL was possible.
So now I'm online with all AP's, but no further toward my 5.5.x-version. HP is working on the case.
I hope we fint a way to do it, so I don't have to enter all config from scratch on verison 5.5.x...