1) Need to know if you are purchasing an entire map, or just receiving the usual Mapshare update
From the 'trashcan' comment, I would assume you are using a Mac to accomplish this (it only matters on Macs)? Yet you say you used Explorer to back up. No matter.
Here's hoping your map backup is good. We're going to need it. Be SURE you have that backup where you can find it!
If at any point, things do not go as described, or other errors appear, stop and let us know.
Connect your unit. Home will fire up.
Minimize Home (don't shut it down).
Looking at your device as though it were a hard drive under My Computer, format it, using FAT32 format, and not a Quick format.
Restore your view of Home, and using Home, properly disconnect your device with the arrow in the lower right corner of the Home screen, or with the pull-down "Device" tab in the top left of the Home screen.
The unit will likely make some complaints, but let's ignore those for now.
Power down your unit and power it up again while it is connected to your PC.
Home will again discover your unit. It should offer to supply you with the unit firmware (aka Application) which is missing -- obvious, since you just formatted the unit!
... Do NOT accept any other updates at this time -- only the application firmware (ignore QuickGPSFix, etc.)
Allow Home to download and install the the application on your unit.
Properly disconnect your device with the arrow in the lower right corner, or with the pull-down "Device" in the top left of the Home screen.
Power down your unit and power it up again while it is connected to your PC.
Home MAY decide it wishes to update your application even further. If so, as before, accept only that update.
Allow Home to download and install the the application on your unit.
Repeat the above 4 steps until Home ceases to offer any additional application updates.
Minimize Home, and locate the backup you made of your unit. Find the North American map folder (it's the one that contains the cline.dat file you mentioned earlier).
Copy this folder to the root directory of your TomTom.
Properly disconnect your device with the arrow in the lower right corner, or with the pull-down "Device" in the top left of the Home screen.
Power off your unit.
Physically disconnect your unit from your PC and turn it on. What do you see?