Since 2.1 I have not had any problem with crashing apps. The only change I can attribute to this is I now "ONLY" load and install apps from iTunes and sync them over to the phone. This includes updates.
Try a HARD reboot. Press and hold the on/off and home buttons at the same time. You will see a slider to turn off but keep both buttons pushed until the phone shuts down. Wait a couple seconds and then push the on/off button. You will get the white Apple logo and it will stay there a few which will make you nervous. Just patiently wait and soon you will see your unlock screen. This has worked for me when I have had that problem with apps. Good luck!