OK, got a real bizarre machine I'm dealing with.
The symptoms are as follows:
When a DVD movie is inserted, the disc spins up but nothing happens. I haven't actually seen this one, it may spit the disc out. It may not.
When you try to make a call with Skype (audio or video) it hangs. Sometimes it just crashes without any interaction. Sometimes it doesn't even launch properly.
When you launch Pages, you can click on any function or menu item, but you cannot see any text or content on the document. The keys you press and items you insert etc ARE actually being recorded, and if you save the document you can view it correctly in Quicklook, but you cannot see anything from Pages itself. I think this also happens with Numbers.
All software is up to date. Up until recently, the problem was completely consistent except when it was taken in to Apple the symptoms would disappear. I recently observed the machine operating correctly but the problems have resurfaced.
I have found a number of similar sounding issues with iWork, but these were all older versions and older OS and were fixed with one update or another. Not an option this time.
My current thinking is that this is a Quartz Extreme issue of some kind and that it is being temporarily fixed by resetting either the SMC or the PRAM.