MacBook Hangs at Startup

Hi,
I really like my Apple products, but I am not a computer expert. My MacBook Pro is hanging on startup. I don't restart on a regular basis but I have been using Bootcamp for work during the past couple weeks and I have been switching back and forth between Windows and OS X. When I was finished yesterday I shut down Windows, and this morning I started experiencing issues when I tried to restart in OS X. The system starts normally and loads my background image, desktop icons, and dock but then the spinning ball goes on and on. I can move the curser but the dock doesn't expand when I move there and it doesn't matter where i click - nothing happens. I waited 10 minutes then gave up. I was able to restart in Safe mode which allowed me to post this, but most functionality (sound, ability to play any video file, Spotlight, ability to read external hard drives, etc) doesn't seem to be working. I understand this is probably by design. I'm not sure what to do next. After being able to boot in Safe mode I tried rebooting normally and had the same hang up issue. I haven't installed anything new or even a software update recently. The only thing of note was that over the weekend (in OS X) it seemed like my Firefox browsing history had been deleted because I suddenly had to enter passwords into an email and spam filter website because it said I wasn't storing cookies.
The computer is a McBook Pro 2.8GHz Intel i7, 8 GB RAM, OS 10.7.2. Please let me know if you need other info, because I sure would appreciate any help.
Thank you!

Try this: Reboot your machine - as soon as you hear the chime hold down the OPTION key. Select the Recovery partition to boot into. Once in Recovery, select Disk Utilities. Select your OS X partition and Run Verify and Repair. After that, run Repair Permissions. Your hard drive was verified when you entered SAFE boot but let's do it again.

Report back results. You may also have a program that's starting when you boot and is causing the hangup. We can look at that later.