When starting CS:Source or HalfLife 2, you may get stuck at a black screen
where your system seems to be hung or your monitor may report a value is
out of range. This seems to be due to a bug properly setting the Horizontal
and or Vertical Refresh rate for your monitor. To workaround this problem

Start HL2 or CS:Source with the command line option -window

Note: You can set this in steam by selecting the game, choosing properties and
then clicking on set launch options.

Once you are in the game, select your desired resolution, aspect ration and change
the mode back to full-screen. If all is well the game should be at the desired
resolution. Simply exit the game and then remove the -window option from the command
line and restart the game.

If you are still having problems please file a trouble ticket with technical support.