I downloaded a new wallet on a new machine then tried to load the backup wallet.dat onto it but without luck.
What happened? Same error?
Also, are you running the correct wallet version?
Yes same error and yes my wallet was encrypted!
Version of Windows 7, 8 , or 10 ?
What Antivirus are you running?
Are you able to get a new mint software installed and synced before you try to put your old wallet in it?
If you are able to get a new install working, but it only crashes when you add your wallet.
Then your Wallet.dat could be corrupt, try the last wallet backup instead and see if it works.
If you can't get a new install working , their is something conflicting with it.

FYI:
Quick Tips
Here are some Windows things to try,
Sometimes left over temp files cause a problem:
1: Delete Temp Files
http://howto.corel.com/en/p/How_to_delete_temporary_files_from_Windows_82. Try running windows in safe-mode with networking .
http://www.howtogeek.com/107511/how-to-boot-into-safe-mode-on-windows-8-the-easy-way/If Mint works in safe mode, then their is a driver conflict with something in normal startup.
(Their have been some reports of issues caused by Google Chromes update service, and Firefox's update service with other coins.)
If Safe mode works , and neither update service is in your startup, run a scan with Malwarebytes and Kaspersky (
http://www.kaspersky.com/antivirus-removal-tool?form=1)
to see if they pick up any trojans.