So i've jailbroken my 3GS with blackra1n. No problems. Downloaded cydia and rock. No problem. Get the sources you need on opening that cydia app. No problem. Download any app (ex. winterboard, cydelete, bosspaper) and the iphone crashes upon reboot. The only way to bring it back to life is to restore it through itunes. I've tried a forced reboot by pressing the top and home keys. I've tried with both cydia and rock apps. And each alone. But everytime i get the same result and need to restore the phone.
Any advise on what i should do now would help me a lot.