I had a similar error during a restore except it was "unknown file type I".  
This was the result of
attempting to backup a filesystem larger than 1 TB in a single stream.    The 
files were backed up
to tape just fine but NBU could not find them after the 1TB mark was reached.  
This is a known
limitation w/  NBU 4.5.   What are you trying to restore? What version of NBU 
are you running?



11/2/2004   11:27:57 AM nwrs011b    Warning     Retrieve    unknown file type I 
encountered,
continuing to process file /DATA02/ (size 0)
11/2/2004   11:27:58 AM nwrs011b    Critical    Retrieve    expected
file/DATA02/DATA/folder1/subfolder1/file1.txt, found file /DATA02/

11/2/2004   11:28:00 AM nwrs011b    Error Retrieve    The following 
files/folders were not restored:
11/2/2004   11:28:01 AM nwrs011b    Error Retrieve    UTF -
/DATA02/DATA/folder1/subfolder1/file1.txt
11/2/2004   11:28:02 AM nwrs011b    Warning     Retrieve    Restore must be 
resumed prior to first
image expiration on 10/30/2005 08:30:07 AM
11/2/2004   11:49:04 AM nwrs011b    Warning     Retrieve    unknown file type I 
encountered,
continuing to process file /DATA02/ (size 0)
11/2/2004   11:49:05 AM nwrs011b    Critical    Retrieve    expected
file/DATA02/DATA/folder1/subfolder1/file1.txt, found file /DATA02/
11/2/2004   11:49:06 AM nwrs011b    Error Retrieve    The following 
files/folders were not restored:
11/2/2004   11:49:07 AM nwrs011b    Error Retrieve    UTF 
-/DATA02/DATA/folder1/subfolder1/file1.txt

11/2/2004   11:49:08 AM nwrs011b    Warning     Retrieve    Restore must be 
resumed prior to first
image expiration on 10/30/2005 08:30:07 AM

Vincent Mase
Perot Systems