No sound making/recieving calls + not ringing

[blankman]

Hi. I am having a problem with receiving calls on my i phone 3G.
Firstly it does not ring and then if I do realize I'm receiving a call and answer it, there is no sound at the other end and they cannot hear me.
To get over this I have to turn to the phone off and on again then it works as normal. This has happened a few times since the 3.0 update
My phone is jail broken using redsn0w and ultrasn0w, and have also installed many further apps from cydia.
Has anyone else had a similar problem. does anyone know of any 3rd party app that could be causing this.
Thanks for you help.