Hi there, 
I just installed Forge 9.11.1.965 for 1.6.4 because some of my mods were outdated. When I press 'play' on the launcher window, it disappears like it would normally do but then reappears. Apparently it crashed but there is no crash report. I can only guess that Forge failed to load. 
  
Here is the link to the ForgeModLoader-client-0.log file. 
  
http://pastebin.com/rpBhmUx9 
  
Thanks in advance for any help 
  
Kalinco 
  
EDIT: I tried to launch it without an empty mods folder and the same thing happened.