Ran into the following problem, still not too sure what caused it but this seems to have fixed it:
cannot generate tempfile `/home/chris/cartsite/tmp/cache/assets/sprockets%2Fd585a06e2ee6203ccb04c8b84150d14d20120804-8682-7q77nb-9'
Just run the following:
$ rake tmp:clear
Let me know if you come across the cause, I’d be interested to know.