I just bought a Galaxy and I have 2 sim cards right now Tmobile and At&t.
Both work as far as calls and text.
But when I try to get emails, go to the market, or browse the web it gives me a network error while trying to sign into gmail. I know I am typing in the correct password. This only happens when i'm not on WIFI
When Im connected to WIFI i can receive emails use the market and browse the web with no problem.
I believe its some kind of setting on the phone but dont know?