Clean out your system's temp folders and delete any leftover PS restore and page files. Also check your document templates and presets folders. Sometimes crashes produce fluke file remnants and PS gets strung up on them trying to restore something that isn't there.
I'd agree with Mylenium and to further than point, when you next open Photoshop go to Edit > Preferences (or Photoshop > preferences on a mac, I think?) and check your performance and scratch disks settings to see if something looks amiss to you. I've had a few issues with a temp file being created on an external hard drive I was using as a secondary scratch disk.
Failing that I'd go to the extreme and unistall Photoshop, run something like Ccleaner, restart your machine and re-install Photoshop again...I know that's a pain in the trunks, but sometimes looking for a 'quick-fix' tends to take longer than just starting fresh again.
Hopefully you get it sorted
Thank you for the reply. In the end I uninstalled and reinstalled and that did the trick.