Annoying "Errors running builder 'Android Pre Compiler' on project" dialog

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http://stackoverflow.com – I keep getting the following error pop-up every now and then on my Android project on Eclipse 4.2.1: Title: 'Building workspace has encountered a problem. Errors occurred during the build. Message: Errors running builder 'Android Pre Compiler' on project 'xxxx'. java.lang.NullPointerException FYI, my project has .svn repositories and uses 4 external libraries (that seem to be fine, no errors). I'm using Android 4.2. What could be the issue here? :( (HowTos)