EMERGENCY: Files lost

Suddenly (I do not really know why and how) I lost access to a folder located
in "My Documents", where over 3.000 photos were saved.

When I click on the folder, I get an "access denied" message. On properties,
there are only 30 Mb of data shown for that folder. That would indicate that
I simply lost all my photos!

Photoshop can not "see" any photo contained in that folder, nor do any other
software. I ran a checkdisk (full), without any change in results.

Any idea what may going on and how to correct it?

Reagrds.