This is weird one, but I have noticed it on two workstations so far;
If I am inputting numbers and use the - (minus key) Autocad MEP reacts like I am hitting the ALT key and bringing down the file/home menu at the upper left corner of the screen. It doesn't seem to happen all the time, sometimes it just works fine, other times I have to actually click down on to the command line for it to work like a normal - key.
I have seen this behavior on two computers here so far. Has the minus key been remapped by default or something?
definitely
if you switch ribbons on and enlarge it to fill the whole screen.... the bug will be gone