this is just a minor bug report - I'm mostly sharing this for others who might run into the same problem.
* when using Sublime for the first time with settings created on another machine, the platform identifier was empty
* because of this, Sublime tried to locate the keymap file at Default ().sublime-keymap
* deleting Packages/Default/Startup.cache and reopening Sublime on the second machine first made the problem go away
I use Sublime on two different machines (Macbook Air and iMac, both running OS X 10.8.2) and have them share their settings through Dropbox.
To this end, I have symlinked ~/Library/Application Support/Sublime Text 2/[Installed Packages|Packages|Pristine Packages] to their respective locations in my Dropbox folder.
The settings files where created by Sublime on my laptop. When I first launched Sublime on my desktop, I was unable to modify my keyboard shortcuts, since Sublime tried to locate the preference files at Default ().sublime-keymap.
On a hunch, I deleted the Startup.cache and restarted Sublime on the desktop. The issue then disappeared; I can now use the shared settings on both machines without issues.