Seems that the problem is solved in the latest release of the Visual unlock: http://www.navitotal.com/forums/showthread.php?1227-Visual-Mio-unlock-shell
Basically all you have to do is to replace the toolhelp.dll file from visual.ins/system/ with the one posted here: http://www.navitotal.com/forums/showthread.php?1227-Visual-Mio-unlock-shell/page12 (post #112) for Win CE 6 devices.