Mathematica version: 9.0.1.0
MacOSX: 10.9.1

I first tried to copy it to my new machine but that didn't work too well, so I downloaded a fresh copy and that's when the trouble began.

I've returned all settings to default--no change.

I heard of a case in which the kernel was dying on the alternate evaluations and just appeared to hang.
Does Activity Monitor show the kernel continuing?  (Be sure to track the regular calculation kernel;
the front end launches a utility kernel to do little tasks for it.)

If you launch the MathKernel by itself, can it perform multiple evaluations of these inputs?
In Mac OS X, 
- hold down the Control key and Click on the Mathematica application (.app) 
- then select "Show Package Contents".
- In the folder that opens, open the Contents folder,
- then the MacOS folder. 
- Double-click the MathKernel icon and a stand-alone kernel will launch.
This is a plain-text interface.