It seems to have been broken between 1217 and 1218. That is, when I type #in and the list box suggests the two possibilites of #include <> and #include "", I can't use the arrow keys to select one of them.
BTW: Yes, I know you skipped 1217, but somehow it must have been posted for a bit because that's what mine reports for its version #.
Are you saying the arrow keys don't work, or the arrows in the scroll bar? We just want to confirm since we cannot reproduce the problem.
The the suggestion listbox appears with two entries, down arrow should select the second entry. Up arrow means, "give me a complete list of suggestions." VA X doesn't have anything better to offer so the listbox clears. Perhaps this is what happens for you.
We have other fixes for #include completion in build 1219. If you still have trouble, wait for that build. It will be available this week.