Ok, this is the 2nd time I've explicitly seen this happen.

I'm copying a large file (1Gb) to a second pc's shared folder.

As that's going on I also start to copy the file to a 2nd hard disk on
the local pc. This 2nd copy finishes much sooner than the first going by
the "details and amount left to copy and speed of copy" dialog.

Thing is when this 2nd copy to the local hard disk finishes so does the
networked copy. e.g. both dialog boxes disappear and both copies appear
to have finished correctly!!! The networked copy is obviously not
correct when one tries to play it and in fact Explorer cannot even
display it's playtime length. Do another copy by itself over it and this
copy is done correctly.

Anyone else ever notice this behaviour?

Anyone got any ideas why it happens?