problem with Authorize payment module

[eptx]

I am using 1.4.6.2 with the new 1.5 theme. When I try and process a credit card it is declined by the processing bank as invalid expireation date, I checked with the gateway company and they say this is happening because there is no separator between the month and year. How do I fix this?

 

Also when I submit this transaction I get no indication of success or failure, the cart just jumps to the first page of the cart entry.