MyBook Studio II showing raid error/ missing disk but working fine?

I’ve had trouble with a MyBook Studio II ever since I upgraded to Mountain Lion.  Most issues are resolved, just one left. The MyBook randomly reports that there is an error - the light flashes! I look at the WD manager and it shows a green dot next to the drive name, but a red dot next to the Raid Status which it says is failed.

I open the drive manager and it states one of the disks is missing and that I need to replace the diak.

The Info tab shows Disk A as faulty.

However, if I click the drive Icon on the desktop, it opens finder and I can access the files!

Is there really a fault on the drive, or is this a Drive Manager/ Driver issue?

If you have the my book in a RAID 1 configuration you should be able to still access your files even if one of the hard drive is faulty, so you provably need to replace Disk A. Check the link below for the steps to replace it.

Thanks for the reply. The drive is actually set up as a RAID0 stripped array, which is why I’m concerned this is a driver/ SW issue and not a real drive issue. I’m about to put the trigger on buying a new drive, but don’t really want to spend $100 and find I still have an issue. 

I’m still looking for a solution to this. I was copying a file today when the DriveManager SW put up a window saying the drive was faulty. Opening drive manager says that DriveA is missing, but the file copies without any issues. This sounds like a FW or DriveManager issue but I am running the latest of both.

I have 2 WD Green 2TB drives inn connection is FW800.