It seems the window titlebar doesn't update when using save-as to network if the existing file is local (at least here at work . This is under Windows Vista. Steps:
-create a new buffer
-type in "C:\foo.txt"
-type in Q:\bar.txt (or a drive letter you have : )
Result: The buffer tab name updates, but the windows titlebar doesn't.
Note, you have to type in the path in the steps above, not browse using the mouse/gui.
Tested with builds 2119 and 2120.