On Wed, Feb 14, 2007 at 10:49:16AM -0500, fredex enlightened us:
one of my co-workers who uses fc4 on his desktop was able to mount it on his client, and it is still mounted from other (non-linux) systems in the server room, so it looks to me like a problem on the client machine. since the problem appeared only after the latest kernel update, it seems likely to be related to that.
Have you rebooted into an older kernel to confirm this is in fact the case?
Matt