Right, thanks got it now. It's as Boki surmised in his reply but i just wanted to be sure.

The only way to remove those corrupt files is to reformat the internal memory. First copy everything else other than the zero size files to a save place on your computer as a backup, then use ONLY [Only registered and activated users can see links. ] to format the internal memory in FAT32 - Don't use any other method, not even the Windows built-in tool in Disk Management. Garmin devices can be very picky about the format and (to mangle an old saying in rhyme) "There's more than one way to format in fat".

After you've reformatted, copy back your good files and then source known-good IMGs to replace the corrupt ones which will restore functionality.