Excuse the plain text on this one, Posting via BlackBerry. My colleague has been addressing issues with File Manager and has just had this feedback which I thought you may find helpful if you use File Manager or are thinking of upgrading to 4.5 if you have not done so yet.
“…Appears to be an issue (causing this specific error message) when running a device with 4.5 OS and connecting over BES/MDS when running BES version 4.1.6 specifically. (There have been a few reported cases of this relating to other applications as well, specific to that device OS and version of BES).This is something that we are looking into, although unfortunately I do not have a precise ETA on when this may be resolved.”
The error in question is a Handler Type error, I have experienced Two similar errors since upgrading to SP6.