Vista - Files can't be found when I browse to attach them, even though they are still there

Occasionally, when I try to attach a file in gmail, I browse but cannot find the file. I open the file through MS word or what not, and trace where it is saved to, but when I try to repeat that through gmail browse the file does not show up. It has dissapeared even though I can find it by going through the program or folder directly on the computer. I just can't find it to attach it.

I have not had problems with the files disappearing permenantly or failing to attach if I find they show up in the folder when I go to browse.

This is driving me absolutely bonkers! Last time i saved a copy of the file to the desktop directly and attached from there, but I don't want to be dealing with this. I have only had this problem with VISTA, and only a few times in the several weeks since I have had the new laptop. I run X64, and it is the standard version that came with my HP.

I have searched online and have not run across my problem, but if someone has asked it please disregard and provide a link.

Thank you!