Cant add music files to iTunes

Hi there. I have iTunes version 9.0.2.25 and unable to add music files to the existing list. I recently formatted my computer for a fresh start (which I have done previously with no iTunes issue), re-added the folder I have all my music in for iTunes but the new files won't add. It adds the 443 music files that I had on iTunes prior to formatting my computer but won't add any new single files when I use File -> Add file etc. as I did originally before the format.

I have googled the issue and there are a lot of people with the same problem but the forums have no answers.

Could somebody please help me with this problem as it is on my iPhone 3G which is an integral part of my work and public time.

Regards
Ross