I upgraded to 0.36 from 0.35 and then lost access to the admin panel.. Meaning that somehow my password got reset. Website was still working. I'm quite sure it has to do with the fact i did not reset all my settings, basically i blindly installed the upgrade and did not check here first.. That I now learned!
I rebooted the router in failsave mode and reset the root password. But that did not solve it. Also tried to upload the last firmware again but couldn't mount my usb stick. Not the usb stick with the website but just another one with the firmware copied on. I started the router normally. I tried to format the usb stick in dos, ext4 and ext2 but all file formats where not accepted by the router ("mount: unknown filesystem type 'ext2").
So still puzzling. Will try more but all tips are welcome!