Broken Portal in BPM v8

Don't ask me why.. but if you enable debug on your Mashup Config Service (Admin Console > Resources > Resource Environment > Resource Environment Providers > Mashups_ConfigService > Custom properties > isDebug = true) it brakes the BPM Portal (blank screen and half blank header - see below)
 


 You'll also notice a bundle of errors in Firebug, the 2 key ones (I suspect) are shown below






...neither of these errors appear on the working portal (although I should point out that there are no shortage of errors reported in Firebug which I can only assume are "normal" and do not appear to affect the Portal's functionality)

Set this property back to false and it'll magically start to work...
I understand when set to true an uncompressed version of Dojo javascript libs are used. Why this would break things is a mystery to me though.