This error message is the OS's way to saying that your MBP is having a problem managing resources. In other words, one or more application that either conflict or there's too much activity for your computer to handle at once. This message has happened to most users.
How do you fix this? I'm afraid to say, there aren't simple fixes, since I don't know anything about your system, your applications, or how you use your MBP. But there are some ways you can track down the most likely culprits:
1. Make a log. Whenever a program quits unexpectedly, document the application involved, the other things you had on at the same time, and the time. With this basic info, you'll have the basic data to begin investigating.
2. Get RAM. If you have 2gb RAM, that's the problem. Upgrade to 4gb RAM minimum, and more if you feel you require it.
3. Update. Make sure your MBP has all the latest updates, even for third-party applications. Developers write applications to avoid errors like you're encountering.
4. Diagnostics. Go to Disk Utility, and perform a preferences repair. Reboot.
There are other potential solutions to this message, but begin with these four. Post if this was successful or not.