If the third party apps are crashing, it would be a issue with memory management. Is it a 8GB iPhone with full memory, or is there nothing but a few apps and a few GB's of memory left.
Could be an issue with the installs of the apps, too.
As for the person that can't get his apps to work, he never mentions in the copied post if the phone was jailbroken or not, or if the phone had been dropped or what. I find it hard to believe that the lack of radio signal in the phone is not allowing apps to load, unless the radio is using up all of the processor cycles to try and acquire cell service. Can't imagine how hot the phone would get if that happened.
Could the phone be in airplane mode and that be the issue of no cell service? Does it say no service in the upper left corner, or show a small airplane? Just questions to try and help out, don't be offended, I am not insulting your intelligence, but the questions need to be asked to troubleshoot properly.