Microsoft Office 2008 Problem/Key Error

I updated my Microsoft Word last night, after the update installed it needed to restart. So after restarting, I went back into it and now it's giving me this error:

"Office for Mac has determined that your product key is not valid. To use Office for Mac, you must enter a valid product key"

And it gives me this website Help and How-To for Microsoft for Mac Office Products | Mactopia

I've had this product over a year and never had any problems with it, and now I can't use it and I don't have the product key for it anymore. And I've followed this website with no help at all; it'll let me re-install but when I try a key from the internet(as I don't have mine anymore), nothing happens it doesn't even say that it's wrong or nothing just stays at the same page.

Any help is very appreciated, the sooner I get this fixed the better as I need to write up something for work in the next few days

Ok, I think I found it and it works now. But turns out that I wasn't the only one with the problem, as this site here says, there's been others that had the same problem after an update.
Microsoft Office 2008 Service Pack 2: Update Issues - MacFixIt

pirate keys by any chance

Did you purchase a valid license for Microsoft Office 2008 or is it a key from the internet?