Imac boots up into "text Mode"

Hello Folks please can you help me?
I have recentely bought a second hand imac early 2010 model.
I have upgraded to Mountain Lion and I am very pleased with it.
It has worked fine until yesterday when I booted up from cold the machine came on in a dos like mode long stream of text commands ending in. To log in to windows (or equivalent) type exit, then a few more lines of text appear and it starts normally. This morning the same thing happened.
Have I altered its boot up mode somehow? How can I make it boot straight to windows type mode please?
Many thanks for any help.
John in the Yorkshire dales England

 

Hello Mike

Yes it is very strange sometimes my machine will boot into what i call windows but now and then into verbose mode like you it did not happen with snow leopard and yet there are not many complaints about this problem!
Let me know if you find the answer!
Best wishes John