Won't display call options or let me call people? Help?

I got a 16GB iPhone 3G for christmas.
Around two weeks ago my brother downloaded cydia on to my phone and winterboard off that.
I got bored last night and started downloading some stuff (ringtones etc..)
It was fine today, until i rang a friend up earlier, the phone went back to my home menu but i was still in the call and the green bar across the top that you can tap on to return to the call with won't return me to the call. I've tried clicking on the phone icon and the keypad appears but i can't do anything with it and it takes me back to the homescreen. I can still call people from my contact book and recieve calls but i can't access the screen to hang up, hold etc.
:/

My brothers iPhone is still working perfectly fine though?

Anyone else had this?

I was thinking of restoring the factory settings but does that delete all of my texts, contacts, apps etc.?

Or is there another way of fixing this?

Thanks in advance, replies are greatly appreciated.