You must enter preboot mode and load kunix's cure, remove maps and reload original firmware. Neil was faster
Spoiler: preboot in 62
Pre-Boot for navigators GPSMAP 62 (s) (c) (t) 78 (s) (c) (t):

1. Turn off the navigator.

2. Hold down arrow "up"

3. Turn navigator holding the arrow "up"

Note: "You can also hold down the" Enter "