To clarify, this issue can be readily demonstrated in SQL Prompt 18.104.22.168.
Open Query window in SSMS 11.0.2100.60
CREATE TABLE #Table1 (mykey INT, yourkey INT, thekey int)
CREATE TABLE #table2 (mykey INT, yourkey INT, nokey int)
FROM #Table as T
Now pretend you know these tables and you know how they appear in the list. As soon as you type JOIN and press the space bar, SQL Prompt will draw a selection box. As soon as you see it pop, you press the down arrow twice to select the second item from the list (#table2) and then tab to select it.
You see the highlight first highlight the first row and you expect it to highlight the 2nd row so you press tab shortly after pressing the down arrow the second time. But what happens is that a tab is entered in the screen, and the SQL Prompt selection box re-draws itself to the right slightly and you can see the selection leave the 1st row, never making it to the 2nd row.
Now if you plod along and go slow, this issue is not exposed. But if you go rapidly, it occurs.
Note this is a behavior change from previous versions (don't know when it changed) as I know that for a long time I was having no issues, and then one day I started having issues. Most often it occurs on the join condition, since you get used to the join you want is always the second one it suggests. It's almost like it is not seeing the 2nd down arrow keypress before it gets the tab or it's missing the 1st down arrow keypress and only acting on the 2nd.