Montana software 5.60 was buggy, news here
[Only registered and activated users can see links. ]
and following.
Oregon 600 had the same, then fixed.
[Only registered and activated users can see links. ] post 127 and following.
Some devices got bricked too with these firmware. Both (Montana and O600 sw have been withdraw from Garmin server after few days)
Montana (WebUpdater) software version 5.60 (withdrawn by Garmin on Feb 3
Be careful to reverse to buggy previous firmware.
Newer Montana and O600 firmware don't have protection, so we don't need any workaround actually.