Internet Explorer Error 8007ffff

When I try to save a picture on a web site thru IE5, I occasionally get this error:
“Could not complete the operation due to error 8007ffff.” I have to reboot if I get this message.
Does anyone know what it means and how I prevent it from happening?
We have a dozen users doing the same thing, and it only happens on a Dell Dimension L566cx running Windows ME.
Thanks for your help!