This happened to me four or five times yesterday. I was using native apps (phone, SMS) when I noticed my clock had been replaced by "Safe Mode". Upon exiting the app I got a popup saying I was operating in safemode because there was a mobile substrate failure and the springboard had crashed. The springboard was grey behind the icons but all the icons worked normally. There was a lot more in the popup but basically I had to respring to get things back to normal. Has this happened to you? I did my jailbreak with my Mac this time but other than that nothing has changed from any other time I've done it. I restored last night because it was starting to get annoying. Guess if I decide to JB again I'll be getting out the ol lappy.