Since 1216 or 1218 I'm experiencing invisible suggestions. In the following example I typed "m_b" and got: then typed "E" (or "e") and got the invisible suggestion. Note that if I press Tab or Enter it's accepted correctly: What's interesting - when I press spin up button with mouse, it gets kind of scrolled to show: Note that pressing up arrow on the keyboard doesn't scroll it, but changes the suggestion list to a completion list.
I got similar (or maybe not?) problem. List box opened with one suggession, but it was not hilited. Pressing Tab, Enter didn't do anything. I had to use arrow key to hilite line, then it worked ok...