Thanks guys. Interestingly enough, I was able to transfer all of my midi file from the problem partition to another partition. I could even add more files to the partition. I then formatted the faulty partition and transferred the files back - no problem. I can now add files too. This has happened before... it's been a month since the last time I formatted this same partition and did the file transfer thing and it was fine until now, allowing me to add files with no errors.

I have a second 9000 Pro with the same hard drive, files and directory setup and it's never give me a problem. So my gut feeling is the drive is going out. They aren't expensive so I'll get another and swap it out to be safe. I appreciate the feedback.