You just can't seem to throw enough memory at Vista.
There have been a number of issues that Vista users have reported relating to copying and moving data, especially large numbers of files. Often there can be multiple errors at play making it difficult for Vista users to track down the problem, in fact very often there is little indication that file copy operations haven't completed correctly. It's only when the user checks the number of files in source and destination that they realize they have a problem.
These don't have to be large files and the problem can also occur when copying smaller groups of files that in total exceed 16,400 files between reboots. Following the "Out of Memory" message a range of other errors can occur such as menus and tabs disappearing within the Windows environment and even reboots and BSODs are reported.