I just updated to the new version and now the alt-o shortcut for Switch Header/Implementation is not working. The option in the menu is greyed out as well. I am on Windows 7 64 bit. I do have a project and there is a matching header to my source file with the same name (.cpp and .h).

strange… it’s works well on 32-bit Vista.
Does http://www.sublimetext.com/docs/2/revert.html fix it for you?

Reverting my settings did not work, however I realized I accidentally installed the 64 bit version of Sublime to my x86 program files folder, which apparently breaks switching header and source? I re-installed to regular Program Files and it worked (And also tried re-installing to x86 to verify that was the problem).