Jailbroken Iphone doesn't allow different SIM card
I'm travelling overseas, I had my 3GS iphone but I decided to go with an international SIM card to save on horrific roaming charges. Unfortunately, everytime I try to put in the international SIM it says SIM FAILED, however my friend has the same model iphone, jailbroke his and is using the same companies international sim card and his works fine, I swapped our sim cards, mine always says SIM FAILED and his works with either sim.
So long story short, my iphone doesn't like new SIM cards, is there something I can do to fix this?
Thanks for any and all help, much appreciated as overseas not being able to contact anyone sucks =\