I've spent the past 2-3 hours today and yesterday looking for a reason why ADT won't generate my R.java file. I've gone through cleaning, making sure SDK versions match up, making sure I have everything updated, and checking over my XML files.
The XML files don't have any obvious errors, but I could be wrong. Haven't touched Java in years :)
Note that this is a completely brand new install of ADT, and the error appears immediately after I start a new project, before I even change anything. I've tried this on 2 PCs to eliminate some weird path problems on my work PC. Nothing still.
I've gone through all the tips in here, for example: "R cannot be resolved to a variable"?