This is happening because when you press shift, Visual Assist selects the underscore so you can write something like: mVar. So in this case, the underscore gets overwritten. But if you accept the listbox, your selection (the underscore) gets replaced with the listbox item.
The workaround is to release shift before pressing enter.
I have found another bug in autocomplete (I suppose unrelated): 1) Type 'var.mem' 2) Press 'Ctrl+Space' 3) It autocompletes to 'var.member' 4) Press 'Enter' right after 5) It autocompletes second time to 'var.memberer'
I am seeing the same effect here. Thank you for the clear description.
case=66653
Are you seeing a listbox appear, showing all members of "var" when you type the dot? If so, accepting the listbox with Tab or Enter is only a single key press, and avoids this problem.