Can't help with the slow transfer ... I assume you were just after the Mapshare update and not a whole map. I don't see that kind of slow download here, but haven't had to pull down anything substantial for a few days. However, both a slow transfer and corruption can occur as a result of a poor USB connection (personal experience, too).
If at all possible, I would like you to use a rear USB port on your PC, and if possible an original TomTom USB cable.
As for your unit, let's see if we can get things working. We assume 8.083 is at least a valid starting point for your firmware, so let's see how this goes. I will assume your backups were made using TomTom Home.
FIRST .. it is critical that you back up your map folder. We can replace anything else, but not that. So do the following. Make a backup using the procedure at this link >>>
https://www.tomtomforums.com/t17864-how-backup-contents-your-unit-computer-how-restore.html
Now, because of the nature of your trouble, I want you to go out and look and report back how the backup looks vs. what was on the unit.
UNLESS/UNTIL THAT BACKUP IS SUCCESSFUL, DO NOT PROCEED FURTHER!
NOT ONLY WILL WE HAVE NO CONFIDENCE THAT YOUR MAP IS SAFE AND SECURE, YOU'VE PROBABLY GOT A USB PORT OR CABLE PROBLEM THAT WILL CAUSE ANYTHING FURTHER WE DO TO FAIL.
Next, have you EVER purchased a full new map for your device, or did you ever use the "Latest Map Guarantee" that was available to you when you first purchased your unit? If either are true, please check for the following folder >>> "C:\Documents and Settings\[yourname}\My Documents\TomTom\HOME\Download\complete\map" or the equivalent My Documents folder for Win7 or Win8, whatever. In the "map" folder, should it exist, do you find any other folders that start with "North_America" or similar? I'm asking this in the event that the backup of the map that was on your unit might also be corrupt for any reason .. getting my ducks in a row in advance.
Now ...
Plug your unit to the PC. If TomTom Home fires up, terminate it.
Format your unit with your OS just as though it was a disk drive. Format as FAT32, and do NOT use QuickFormat.
Use the proper USB disconnect method (icon in systray).
Unplug and replug your unit to the PC. Allow TomTom Home to fire up. It should note that you need an update .. though it's a lot more than that .. you need an application for your device!
No matter what is offered, accept ONLY the application for update. Allow it to download and install on your unit.
Use Home to properly disconnect your device and then unplug and replug it. If Home offers yet another update to the application you just received, rinse and repeat from Home disconnect through application installation until Home ceases offering updates.
When you are done, let us know what application you finally wound up with.
Once that's complete, and while the device is still connectged, copy the North America map folder back from your backup that you made per the instructions above. Yes, manually copy the entire folder intact to the 330. Use Home to disconnect. Remove your unit from the PC and power it up.
Does it work now?
