If you're an Android application developer, this one is for you -- there's a bit of a show-stopping bug in the ADT plugin for Eclipse when used with the Android 2.3 SDK. Reports are in that after you upgrade your plugin, opening a non-Android library project results in the error "unable to execute dex: null."
The good news is that a fix has just been pushed, and you can now get ADT 8.0.1 and get back to work.
We doubt this is the only bug, just the first one found. In any case, it's nice to see Google and Android developers take an interest. To find a bit more info, check the Android Developers Google group. [Android Developers] Thanks Joe!