Thanks Krileon. My last message was a bit misleading, I meant I had checked the indexes in the users and comprofiler tables. The problem with the edit user screen continued. However following a test on another machine it seems it is browser related. I only get the problem with Chrome, it is fine with Safari and Firefox. I deleted Chrome and all i ts app support files and reinstalled and the problem went away for about an hour then came back. Safari and FF are still fine. Weird, I know!
I'll use FF when necessary and stop worrying about it.