I sorted this out. So for anyone else still on the learning curve with me, the solultion is as noted in my comment. In addition -
aapt = Android Asset Packaging Tool From the Developers Guide - "The Android Asset Packaging Tool (aapt) takes your application resource files, such as the AndroidManifest.xml file and the XML files for your Activities, and compiles them."
The solution for me was simply to delete the error on the 'Problem' window (right click | delete). Then, force a rebuild by rerunning the app. Any remaining problems will now show up and be logged so you can track them down.
Hope this is helpful to others.