I assume you have already contacted Cingular to ensure that the SIM can be used on the 7290.
I have had experiences using SIM cards from other devices that caused serious problems. Specifically, there was no functionality after transferring the SIM card.
Also, you stated that you used the "desktop manager" to wipe it and loaded 4.1. Was that the latest handheld software, or desktop software? In order to wipe the device correctly, you should go to options--security---select any option and click the scroll wheel---select wipe handheld and follow instructions. this option only wipes the messages stored on the blackberry, and will require regenerating the encryption key.
Based on your post, I really feel that this is a SIM/Cingular problem.