we have the same problem here, but whit BE10.0 and Uninstall SP2 for office is not a solution , change the configuration from incremental to full backup is not a solution...
after this steps we get the same erros only whit Windows Vista clients...
what happend whit full backup?, some users here have 2 or 3 pst files from 1.5GB to 2GB, and these backups run to disk, we dont have any library to send this jobs to tape... and the space on HD is a problem...
If we upgarde to BE12.5 this problem disappears?