Downloading Home shouldn't cause the problem. That software goes on your computer, not the unit.
Connect the unit to the computer. Don't start Home. Look at the contents using Explorer. Is there a map folder there (USA_Canada, probably)? If so, is there is a file in it with an extension of .meta.dct?
Also, did you download an updated map? If so, it'll be here in compressed format:
C:\Documents and Settings\yourname\My Documents\TomTom\HOME\Downloads\complete\maps\
So, using Explorer, not Home, make a complete backup of your unit's contents. Then, after ensuring the backup is on your computer, remove all the loose files in the root of the unit using Explorer. Don't delete any Folders or their contents.
Connect the unit to Home and it should offer an application update. Accept it & install. Disconnect the unit properly from Home using the Device disconnect icon. Restart the unit.
Any better?