Another External Hard Drive Problem...Any Ideas?

So I bought a Western Digital 2TB Hard Drive a couple months ago for my mac mini. I have been using it to store all my music and movie files. I also use it for iTunes storage. It is formatted on FAT32.

Everything has been working great until a couple days ago when I went to open a file from the hard drive and the file just disappeared off the screen without opening. I tried another and another with the same result. I attempted to unmount the hard drive through disk utility but was unable to saying to close all applications still using the hard drive, although all applications were closed. I had to physically pull the USB cable to unmount the drive which I know isn't good but I had no choice.

I plugged the Hard Drive back in (tried both USB ports), it did not mount and appear on screen. I checked disk utility and it appears in there. I did a disk error check and disk repair and it said everything was fine. Mounted the hard drive successfully and it was working fine for about 20 min and than files started disappearing off screen when I clicked on them. The hard drive seems to work sometimes and not work other times. 90% not working properly and having to unplug the USB to unmount. Doing a disk check and disk repair isn't even possible saying "error unmounting".

I use the hard drive on my D-Link Boxee Box to play music and movies on my TV and it works flawlessly. I use the same USB cable to plug into the boxee as I use on my mac. I can't figure out why it won't work properly on my Mac all of a sudden. I have tons of space left on there I would like to use. I know of the program Disk Warrior but costs $100 to buy and would only be a last resort if I can't find another solution.

Sorry for the long post just wanted to give as much information as possible in order to get the best feedback. Thanks in advance for any possible help, it would be appreciated.