I went through the very good instructions here to export an Exchange 2010 mailbox to PST:
But I kept getting errors when doing the mailbox export request. I didn't track the error, but I'm about 90% sure that the error was related to the file path I was exporting to. I was attempting to export to a file path of "\\servername\e$\filepath\username.pst"
Once I changed the export path to \\servername\sharename\username.pst - the export succeeded.
Stupid, but something to remember.