Mobi2Mobi GUI v0.10 Released
Made a quick mod to the GUI to support the PERL file directly instead of using the Win32 compiled version which seems to be causing some problems for some people.
Provided you have Perl setup exactly as described by Tommy you will only need to ensure the perl file of mobi2mobi is called mobi2mobi.pl. You just point to the directory with the file in it and tick the Use Perl tick box.
Hope this helps out some people. Let me know as usual if you have any problems.