Photoshop problem

I can't get Photoshop to boot. It was working fine this morning, but on attempting to fire up again this afternoon I can't get beyond the spinning timer. It's loading as usual, but after a couple of seconds of not responding to the cursor as I try to shift it across the screen, the timer clicks in and that's that. Any theories welcome!

Either you have 2 many fonts activated, with one of them causing the problem

If not then try resetting the prefs file
press Shift + Command + Option when starting Photoshop

Many thanks for the tips. The font issue may well be it: I've downloaded a batch of new fonts recently, although P'shop continued to operate efficiently directly afterwards. I'll check it out.