Kernel boot screen on startup?!

[ajf]

Completely separate to my other post, I have got the following twice now when booting from powered off.
If I hold power until then try again it seems OK.

Any ideas?
Could it be because I switch the keyboard on and off when not in use and it detects a key press when I first switch it on?

 

[ajf]

No, definitely not a hack! It's a 2 year old 27" imac with a genuine install of Mountain Lion. Other than what I mentioned with the keyboard I have not changed anything recently that I know of either.

Least I understand what it is dong now so I'll have a bit more of search.