Call Failed error solution
I have of now; checked each and every version starting from 0.90 and 0.96! I got my 3g iphones to work on all of them. I have my guide here http://www.hackint0sh.org/forum/showthread.php?t=61855 (It was for the older versions- Hopefully you wont need to use anything with the latest version)
I must say that 0.96 is by far the most error free version. I installed it through Installer. Wait for it to download. Reboot your phone and thats it! no need for anything.
NOW; my phone was working perfectly . calls in/out data and sms but i upgraded to 0.95 and i started getting the call failed error for outgoing calls. I restored my phone; tried and installed all the previous versions one by one but no relief. Still call failed. I installed 0.96 and everything perfect except for the outgoing calls. So after two-three days something occured to me. I went into settings and then phone and tap the show my caller id settings. It turns out the show my caller id tab was off. SO i turned it ON and voila!!!!! I can make outgoing calls now! I turned my caller id off and tried making calls and started getting the Call failed error again! I have tested it on 4-5 different 3g iphones now and the same result. The show my caller id has to be ON!! and the calls out start working again.