It's not a bug in VB.Net. In fact, it's not a bug at all. It is part of the
.Net Windows Forms object model. I'm not sure why Microsoft decided not to
support this, but I suspect it is due to the way menus are designed to work,
that is, with shortcut keys displayed alongside of the menu text (if
desired).

I do my work in C#, which is why I know it has nothing to do with VB.Net. I
did several hours of research, like yourself, trying to figure out why it
didn't work as it did previously. I believe it can be changed, but it would
require a lot of tweaking to do so. I got the impression that MS wants
developers to follow a more uniform set of design standards, which is why it
would be difficult to change. So, rather than research further, I decided to
"go with the flow" and use the design behavior built into the Framework.

I do wish that Microsoft had taken more trouble to explain this in the
documentation. As both you and I have experienced, a change of this sort can
cause a developer to waste quite a bit of time trying to figure out what
happened, and a little better documentation (read "explanation") would be
extremely helpful. But for whatever reason, they decided not only to change
the behavior, but to hide the information about the whys and wherefores of
this change. In fact, the documentation mentions the fact that you can use
the "&" in a menu text, but doesn't mention why it isn't a helpful or useful
thing to do.