Event ID 333

We have Exchange 2003 in cluster environment in windows 2003. Primary node of the exchange logging error
An I/O operation initiated by the Registry failed unrecoverably. The Registry could not read in, or write out, or flush, one of the files that contain the system’s image of the Registry.
evey minute. after restating the server it works fine 1 or 2 days but after that same erroe. secondary node is ok. when the error start the role is automatially shift to