After getting a new computer and setting up eclipse again, no projects are generating the .R file. The SDK is on revision 22 which I noticed some people had issues with, but setting the Private Libraries checkbox did not resolve this.
The .R isn't generating for existing projects nor brand new empty android projects. The SDK levels between the build configurations and the manifest match.
An entire uninstall of the SDK, and redownloading the Android version of eclipse and SDK didn't work as well. Could it be something with the versions of Java installed on the machine? Or is there some other common cause of the R not generating I missed after searching?