"Out of Memory"?

This is absurd. I was copying files last night via drag and drop and got a message that said "out of memory." The laptop has 2 Gig of memory, nothing else was running (not even Zone Alarm) and the Task Manager indicated that there was plenty of memory available.

I have never had this happen with any version of Windows while copying files. Any ideas? Thanks.

Inspiron 1501, Vista Home, 2 Gig memory