RAID Mirror issue

I have had no problems with the RAID mirror (hardware type) on my win me system for over a year. I am not doing anything different on the computer from the normal, but now it frequently gets out of sync and gives errors that one of the drives is not detected. If I perform a hard reboot it see's both drives agian , and then proceeds to "Rebuild" the array which takes about an hour. Then it works ok for a while, until the next time maybe 2 days later.
Could this be what happens if one drive gets worn out and maybe starts to run at a slower rate ? Would it work sometimes , then not ? The drives are IBM 40 gig, and a little over a year old.
The raid card is a Promise Fast track ultra ata 100.
Thank's

 

Sounds to me as if one of the drives is on its way to the great hard drive array in the sky

I'd look at replacements if I was you