only boots in safe mode

When you can boot in safe mode, that usually indicates that you have something in your login items that is causing a problem. One way to address this is to boot in safe mode, go to system preferences, users and groups, and on your normal login ID, look at login items. Write down what they are, then start eliminating them one at a time, and reboot normally. Fixed? No? Boot into safe mode and repeat.

While you're in System Preferences, there may be programs listed at the bottom of the window .... you want to ensure those are the 10.7 compatible versions of those programs, otherwise that could cause issues too.

This will tell you more about what you're doing with a safe boot: http://support.apple.com/kb/HT1564