Just a thought Carig, if you have external drives attached via USB, CCleaner will clean it too and is very slow.
If not I'd give their forum a shout and see what they say. My CCleaner has some issues and took 3-5 minutes to run less than 10MB of data. It somehow fixed itself, but I don't know how.
How big are the compressed files. If you have Font Cache checked for cleaning, uncheck it.