I think its your security settings. Check them in the properties and make sure your user has 'full control'. Best to give every user full control, including registry and computer installers... I you don't have the sufficent rights, glest can't get the file right...
May also have to do with appdata... If the rights aren't correct, glest tries to use the appdata, and if you delete the file from appdata without the significent rights, dunno what could happen (probably nothing, as it is SUPPOSED to recopy it, but who knows).
Probably easiest to reinstall before trying my method to make sure that there was no corruption in the file. Redownload it, install, try. If it doesn't work, my method is VISTA based, but should work on XP.