I am having problems getting it running on my n78. whenever i open it it just freezes and my menu stops responding (red phone is the only way to exit menu). The rest of the phone still works but the menu freezes and Garmin XT doesnt open. I currently have no maps installed (only the v4 basemap.).
Garmin Mobile XT on N78
Try removing it and reinstall it
Garmin XT hanged on my phone the first time I tried it but since then it hasnt done it, not sure why though
Perhaps the file you downloaded is corrupt?