Every once in a while, I received the above error. I found another post which I was unable to reply to with the same problem as me. What can only be described as "strange Chinese characters" are in the filename and BE will not back it up. The files do not exist in destination as named.
I am currently using BE 9.1 with the latest service pack. The problem is not limited to one server and sometimes the error goes a week between failures, sometimes a few days. In each case, there is no "pattern". Sometimes, if the error occurs more then one backup in a row, running a "chkdsk /v" on the offending drive will stop the problem from reoccurring.