Could you take a screen shot and upload it and show the displayed error message please?
To take a screen shot you would click the "Print Screen" or PRNT SCRN button above your arrow keys
a website you can upload it to would be http://imageshack.com
and then page the link of the JPG file in your next post
Have you ever used jailbreak software? - be honest
Do you have any security software installed - If so Disable it - Each and every part of it..
If your unsure how to disable security software follow
http://support.apple.com/kb/HT2292 - this will show you how to disable all 3rd party software -I usually keep my computer running like this since it runs much faster
No I actually haven't. The software on my pc is all legit. I have a free version of avast internet security running on my machine, which I have deactivated, restarted and the software is now busy downloading - Thanks a million!! Thought I was going nuts!! Have a sweet machine with no speed problems, that's SSD for you.