can't create a new folder.

I have the 120 gig H/D installed so I've been saving my material to folders. But the mpc will not let me create new folder. I have 3 folders created and it won't let me create a 4th folder. Is this common?

Did you format the harddrive before? Which OS version are you using?

I reformatted and updated my os its seems to be working so far although when I stored my hard drive contents on my mac during the reformat update process I lost some material. Thanks for the help. It was driving me insane.