I guess if you were using Microsoft, it probably didn't give you the 'file name' did it? I know 98SE and some of the early Windows OS's can't use names over 12 characters in length (you probably know that already). Maybe one of the memory locations was corrupted, It can happen!
Shut it down and try rebooting. If you still get the error then just scan (scandisk) through the data folder and check all the folders and files for readability by the drive.