No access to ReadyNAS Duo v1

I have a ReadyNAS Duo v1 (RND2150 v2) which have been working fine for almost 3 years with my Win7 PC and it worked on my XP machine before that.

Some days ago my mapped network drives stopped working but I have only tried to solve the problem today. That appears to be more difficult than expected and I have search the forum for a solution.

This is what I know:
- the IP of the readynas is 192.168.1.13 according to RAIDar and all indicators are green
- I can ping 192.168.1.13 from my router/cmd with success
- In RAIDar I can make a rescan and even a Locate and the ReadyNAS responds to the locate by blinking lights on the ReadyNAS
- In RAIDar I cannot Browse the ReadyNAS (Error message: "Windows cannot acces \\192.168.1.13") and I cannot run a Setup (Error message: "this webpage is not available" when trying the address "https://192.168.1.13/admin/"
- the ReadyNAS performed a synchronisation during the night but this did not solve the problem
- Yesterday I updated RAIDar from version 4.3.4 to 4.3.8. I have uninstalled the 4.3.8 and reinstalled 4.3.4. No changes
- RAIDiator version is 4.1.10
- I cannot access Frontview from any of the browsers I usually use (Chrome and IE)
- In March I upgraded the disks to two WD Red WD20EFRX 2TB disks but they have been running smoothly since
- I cannot access any shares from Windows Explorer. Both shares have "Disconnected Network Drive" indicated as type and trying to open either share results in an error message stating that "The network path was not found".

Does anybody have any idea to what might be the problem and a solution? To me it appears as if the ReadyNAS and the disks are working but that the is some kind of network issue. I have read something about Microsoft Networks File and Print sharing could pose problems.

Any help is appreciated.
Thanks
Henrik