system error when copying file

Tried to post this before and don't know if it made it, so
here goes again...

When pasting a copied file from a:drive to My Docs,
receive following error message:

"Cannot copy (any file). The system cannot read from the
specified device."

The file can be seen and opened fine on the a:drive, so
a:drive appears to be working OK.

Can this be easily fixed? Off-site employee trying to work
on project, so please reply soonest. Thanks!