Secure Element not responding!
If you have a Nandroid backup of a version of Wallet that worked, try restoring to that. Otherwise, you're screwed unless you get a new device. The Secure Element in your phone has now locked you out.
EDIT: research seems to show that Android is not actually enabling NFC-EE, which might be why it can't communicate with the SE. This needs further research.
To try to avoid this, before flashing a new ROM please, please, PLEASE: open Google Wallet. Open the Wallet Settings menu. Select "Reset Google Wallet" from within the app. THIS IS NOT THE SAME AS SELECTING "CLEAR DATA" FROM WITHIN MANAGE APPS!
The Google Wallet reset system will disable it's background services, reset the secure element by deleting the Google Wallet applet (which is what you want!), clear the database, ping C2DM that it is now deprovisioning, clear the shared preferences, clear files and cache, and finally shut itself down. Clearing data from Manage Apps will only delete the database and shared preferences: it will not deprovision, disable background services, and most importantly will not remove the Wallet applet from the secure element.