I asked my son about the question posted by Shom Paul.  Here is his answer...

From: Andrew Norton
Sent: Thursday, November 04, 2010 11:31 AM
To: Patrick & Cari Norton
Subject: Re: listserv question

If "lockup" refers to the condition when a human operator cannot move the third motor, this is a common problem in menu/master programs.
When the NXT sets a motor to "break," it locks the motor, preventing it from turning at all.  To get the motor out of "break" mode and into "coast" mode, use a move block to turn the third motor 1 degree (or something else small) with the end action set to "coast."  Setting the motors to coast should be done between the end of each mission and the start of the next one.  This problem not seen when running the programs individually, because the NXT sets the motors to coast at the end of each program.
The third motor should now move freely between missions.
However, this will cause another problem:
The NXT keeps track of how the motors are positioned, even while they coast.  The effect is that the arm will move too far/not enough in the next program.  The solution is to reset the rotation sensor before running the next mission/run.  This is done using the yellow rotation sensor block and setting the action to "reset."
Andrew Norton
Programmer for FLL team 12, ACME Robotics
----- Original Message -----
From: [log in to unmask] href="mailto:[log in to unmask]">Patrick & Cari Norton
To: [log in to unmask] href="mailto:[log in to unmask]">Andrew Norton
Sent: Thursday, November 04, 2010 11:15 AM
Subject: listserv question

Subject: nxt motor lockups
From: Shom Paul <[log in to unmask]>
Reply-To: Shom Paul <[log in to unmask]>
Date: Wed, 3 Nov 2010 13:35:32 -0400
Content-Type: multipart/alternative

text/plain (24 lines) , text/html (20 lines)

Has anyone experienced situation where a motor would lock up when running a
program with multiple myblocks (and nested myblocks)?  We're experiencing
this problem with our robot's 3rd motor when we run a master program (where
all our missions are in one program), which we don't see when running the
missions individually.  Does anyone have any suggestions?

Will activation of the 3rd motor on a separate track fix this?  Has anyone
found reasons to stay away from using master programs?



To UNSUBSCRIBE or CHANGE your settings, please visit https://listserv.jmu.edu/archives/vadcfll-l.html and select "Join or leave the list".
VADCFLL administrative announcements are sent via VADCFLL-ADMIN-L. Visit https://listserv.jmu.edu/archives/vadcfll-admin-l.html to subscribe.