Unable to access Readynas Duo, Advice Please

I have a duo RND 2110 that I use for my music. It has 2 1TB disc drives installed and has been working without any problems for well over a year. I wanted to add some new music files and was unable to do so. Using the RAIDar utility I can see the drive but the setup and browse buttons are greyed out. The status from the RAIDar utility says "file system check 100%" If i try and access the drive from windows explorer (XP) i get "the network path was not found the connection has not been restored" The drive is connected to my router and the pc is connected to the router via a hardwire ethernet cable. The drive is still showing as my Z drive from windows explorer. The led's on the front of the NAS are as follows:
Disc 1 permanent on
Disc 2 flashing
The act led and blue power led seem to be flashing in a sequence as below
act flashes once blue led flashes four times
act led flashes once blue led flashes three times
Pattern repeats
Help and suggestions welcome please