I currently live in Hungary and here we use characters that are not used in a lot of places.
I tried to do a backup (plain copy to another directory) and any file that had a ő (o with " on top) in the name did not work.
I am using ComodoBackUp_Setup_184.108.40.206.exe
The following is the error message in the log
Error - Copying of file C:\Documents and Settings\Phil\My Documents\motorcycle\Kárbejelento lap.xls
and this is the real filename