blue line running from bottom to top of score with an arrow on the top of the line

Hi,

I suddenly found this in a score I was working on after I tried to change the instrument in the staff, and/or after I decided to hit all the "F" keys to see what they did.

I've attached a screen shot of the line and arrow.

There is a similar line at the end of the score.

Any idea how I can get rid of this?

Thanks very much,

Rob Ryan,
Ottawa