I tried running Left4Dead,but once the game started running my screen went blank and I got an error on my monitor that said "Out of Range Frequency", I have never had something like this before. Especially while playing Left4Dead, everything else on my pc is running just fine. I can even load up Mass Effect without any problems. Does anyone know how I can fix this problem?

It sounds like the game tried to run at a resolution or refresh rate higher than your monitor supported.  Did it just happen for a split second?  What kind of monitor do you have (CRT or LCD?)

I wouldn't worry about it if the problem doesn't continue.

Hmm, sounds familiar. Have you reinstalled L4D recently? For some reason it defaults (I think) to 1280x1024. A lot of users get a blank screen but can hear the audio just fine. If that sounds similar then I suggest changing your desktop res to 1280x1024. If it launches ok after that then you can go into the graphics options and change it to whatever you used before and it should be fine on subsequent launches.

Rub peanut butter on it.  I hear that helps.

I fixed it, the monitor was complaining about the resolution, as I set the launch options to start up at 800x600 the game starts up with no problems, I can even change the resolution in game up to 1280x1024 and it will run just fine. Weird fix, but it works.