Cannot rename/create a Folder on the extended drive

Hi,

I have the following problem.
Our customer wants to create-rename a Folder but
he gets the following error messages:
If he wants to create:
Cannot rename the New Folder. The network Path doesn't exist.

If he wants to rename:
New Folder cannot be rename: It has been used by another process or person.
Close all program which could be used by this file, and try again.

workaround
if he stops the dx service it doesn't help
be if he restart the services it solve the problem for a while, after it begins again.

I have checked the logs, I found nothing. Any Idea?
The disk Xtender is on a MS cluster(w2k3), the archive device is a Centera
Disable Folder Rename Check is Yes

Regards
Zoltan