Did you try typing anything at the Kernel prompt, or was the window inert? Example,
Mathematica 6.0 for Mac OS X x86 (64-bit)
Copyright 1988-2008 Wolfram Research, Inc.
Out= 6.0 for Mac OS X x86 (64-bit) (May 21, 2008)
The Mathematica Front End hanging is due to a (now) known incompatibility with 10.7.2. (It was a surprise for us, too.)