Are you seeing this with all classes? Or only some classes?
So far I cannot reproduce this problem with the String class. Can you try the code:
void testStringList()
{
String strName;
strName|
}
for me, when I type a dot at this point the listbox appears normally, and stays visible.
Can you try upgrading to VA 1616?
If this does not help, does disabling VA via:
VAssistX -> Enable/Disable Visual Assist X
make any difference?