I am not saying this is the correct way to recover your data, just trying to advise!
Start by reading this blog entry
Some NAS Drives run on ARM architecture and normal CPU's cant read the blocks becasue they exceed the filesystems memory allocated to handle these reads.
There are work around obviosly.. but it can be a bit tricky
If they are stripped sets then,
You need both drives to recovery anything sensible. Files and data are scattered on both drives. One drive is useless.
-But if they are mirrored then 1 will do. Sometimes the NAS boxes will not let you run the single drive on its own.. without putting a new one in and resynchronise them... i find it pretty annoying.
You can also try tools like WinHex, or go and visit HDDGuru Forums and read some threads there are really good ones there
If you got some really important data on there and you start feeling uncfortable then you need to stop. There are good data recovery centers out there, for reasonable prices.. if you need help let me know.