Purchase Order Numbers

Hello - I am in the process of upgrading to the current version - which I understand is now 7606. We were at 7014 and currently are running 7514 so I have a few steps to get to the current. However, I have run into an issue that I don't understand related to assigning Purchase Order Numbers. We have been using a letter as the first character of the PO number but when I try to enter this I get a database error [FAILURE :Database exception setting default configuration. Please report the problem to the system administrator, with the Error Code - 1,271,194,940,144].

Any ideas what needs to be done to correct this? We have been using Exxxxx for many years now including with earlier versions of ServiceDesk Plus.

Thanks
Dennis Rhine