Issues with Cellular connection

I have the EXACT same problem with my iPhone 3G.

Just replaced the "main" flex cable due to a broken on/off button and now I get "No Service", but WiFi works.

I've verified all flex cables are connected, and even triple checked flex cable #6.

Anyone with ideas/suggestions?

Perhaps I've used a 3GS main flex cable instead of a 3G one?

PS,

It originally complained about not being activated, and that activation would take some time, left it over night, in the morning it said it was activated.

FYI,

All my downloaded apps close immediately after starting, but iOS default software (like maps) works - very frustrating.