How is everyone else upgrading their 3gs's to 4.2.1 & keeping their ability to unlock..

The way I did it was I used snowbreeze2.2 created a custom firmware that kept my 5.13.04 bb but did not use it to jb

I then put the firmware on my phone then used GP to JB (wanted the bootlogo)

But now Im having problems with invalid sim errors ever since putting 4.2.1 on my phone I have to use another simcard to get my phone to activate in iTunes,even when I restore back down to original 3.1.3

Then once its activated I can not reboot the phone or I'll get the same invalid sim error

Anyone have any idea wtf went wrong..? If I need to replace another sim Im gonna go crazy it'll be my 3rd since getting the phone last summer..