Ok, can someone please tell me why this pops up? I have no idea, but I get these dialogs all of the time now and I have no idea what is triggering them.
Is something changing the file on disk behind the scenes while you have the VI open and are editing it? Perhaps some source code control, or drive mirroring program? Is the file on your hard drive or on a server?
You also get this dialog when moving files on disk (from LabVIEW), and probably when opening two projects with shared code (didn't check).
LabVIEW Programming ((make LV more popular, read this)