Files on MP4 Suddently Can't Be Read

Hi Mates,

Need helps!

I stored some very important files on my MP4 and it has been working well for me for years. All a suddenly, they do not show on my PC. It worked well the night before but when switch on in the other morning, it just showed a blank device. FYI, I am using the antivirus McAfee special edition for AOL.

I've checked:

1.To exclude that it is a cable problem, I checked the property of the MP4 (right click the MP4 root directory and then property), it showed the actual amount of free and used space, which agree with what was found before the problem. That means there still are files on the device but it just could not be shown.

2. It works fine when I made new directory and copied files on it (when connecting it to the PC). The directory and files show and could be read clearly. They could be deleted fine as well.

3. The problem was all files already on it do not show! It looks like a blank device. Some of these files are very important and wonder if there could be helps from you all or tools that I can use to recover them?! Thanks in advance!

4. When detached from the PC, the MP4 works fine as well, all music play well when it is stand alone.

5. Checked the soldering, dry joints or cold solder, they were all good. No loose connections.

6. Changed to use another computer, other USB hubs, result were the same!

Please help. All idea are appreciated!

Thanks and cheers,

AC Wing.