Photoshop 7 problem - saving error

I made an icon and when I try to save it (no matter what format, I've tried everything from .png to .gif to .jpg and everything in between!) it says:

Could not save as "icon.png" because of a disk error


I looked through the FAQ and memories and couldn't find anything that related to this. Has anyone ever experienced this? What does it mean, and how do I fix it???

Thanks in advance.