ZD Net writes about a bug in Windows Vista that causes your system to run out of memory if you're trying to copy a large number of files (about 16,400).
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.
Although the problem occurs where users are running Kaspersky security products, it’s a kernel leak that lies at the root of problem (the problem’s not confined to systems running Kaspersky software, that just that this application seems to exacerbate the issue).
This issue should be fixed in Windows Vista SP1 but if you can't wait that long you can request Microsoft to send you a hotfix>.