Having a totally backwards situation here.

Windows 7/64 bit clients with current beta NW client.
Issue came up that files that were opened by someone else created a
pop-up on the WS asking something like;
"verify that the file exists"

On the server and ALL clients, file caching/oplocks = disabled.

But,, here comes the strange part,
enabling file-caching the client actually seems to help even if it's
still disabled on the server.
Now, with file-caching enabled on 2 test-pc's, the 2nd PC trying to
open a file gets the question;
"the file xxx have been locked for editing by "userxxx"
and then the option to open it read-only, local-copy or message when
it's available again.