@BDangerfield
Unless your device doesn't turn on past the Garmin splash screen and has lost the ability to communicate with a computer in Mass Storage Mode, you do NOT need to load cure firmware such as kunix's GarminCure3 or QuickCure3. In a device that fully boots, weird behavior is usually fixed by a hard reset as was suggested in P#2 (Ensure it's fully off, not just in standby > Hold lower right hand corner and turn on > Follow on-screen prompts). If problems are still apparent, clear its non-volatile memory (Press Speed field on main Map screen > Hold center of Speedo for several seconds to reach a hidden menu named 'Diagnostics Page' > Press on 'Developer Info' and scroll down and select 'Nonvol Statistics' > Press the Menu in top left corner and select 'Clear Nonvol'. Both Hard Reset and Clear Nonvol will clear favorites so back them up first if you want to restore them later but be aware that there's a chance that data may be causing your present problems. Clear Nonvol is more comprehensive than a hard reset so you can just do it instead of a reset.

Post again if you still have problems.