Help Trouble with imac when restarting

Hi I have my Imac nearly a month now and I love it

IMAC 21.5"/2.5QC/500GB/6750M
PROCESSOR 2.5GHz Quad-Core Intel Core i5 MEMORY 8GB 1333MHz DDR3 SDRAM - 2x4GB HARD DRIVE 500GB Serial ATA Drive
GRAPHICS AMD RadeonHD 6750M 512MB GDDR5

BUT

if I go to the apple icon on top left and go to restart it just times out with little round circle going around, i end up plugging power out, then it starts fine,

obviously this is not right, its happened me twice, imac did a software update and i told it to go ahead and restart and it just timed out, that was yesterday,
then this morning i tried restarting it myself and same thing happened
any ideas?

did you do the obvious such as repairing permissions and such? thinking of that as from your description i thought you might be new to mac.
if you need an instruction - have a look here:
TheMacMania - Tips, Tricks and more for your Mac Computer

yep i did that, had seen it on this forum so did it,

did you replace lion files? it nearly does it itself and your own files are not effected so this might help and costs maybe an hour

no i didnt do that how do i go about that ?

It sounds like a software update that you installed has failed. This can happen on occasion if the download becomes corrupt. Since your iMac is still under warranty and you have 90 days free telephone support from Apple, I suggest giving them a call and let them walk you through a reinstall of Lion. That should get you back up running again.

By the way, I highly recommend you purchase Apple Care for your new iMac as that will give you a total of 3 years for the warranty and free telephone support.

hi thanks for all your answers, i went onto apple support and they told me to plug out everything from back of i mac, ie, printer network etc and try and restart so i did and it worked then i plugged everything in singularly and it seemed ok ?