This will only work (and is only safe) when your game client is fully installed and you're just trying to get it to work again.

This should also solve the issue of "Updating game client..." or whatever it is.. frozen screen before the launcher.

Windows 7:

-> Right click Diablo III.exe in your D3 folder and click 'Send to Desktop (shortcut)'.

-> Click Properties

-> Add " -launch" to the end of the field there. An example is below, and also includes the quotations.
"C:\Program Files (x86)\Diablo III\Diablo III.exe" -launch

This will force your shortcut to bypass the launcher and directly launch the game.

I hope this helps.
Edited by Rispetto#1398 on 5/15/2012 8:29 PM PDT