Finally decided to upgrade to 4.4 from 4.3 during Christmas.
I made a fresh install on an old harddrive on my backup machine and then installed the drive in the router.
As router the 4.4 seemed to work as it should but the control panel didn't.
After a lot of troubleshooting I have found that I can acess the control panel for about 5 min after the router have booted whereafter it stops responding even if you are logged in and using the interface.( I can add that the same bahaviour applies to the web server on port 80).
At this moment I have gone through all configuration options so many times without finding any setting that changes this behaviour so now I hope that sombody can give me a hint about what's wrong.
/Islander