I wrote a program for moving robot. i wrote functions for moving forward, backward, turnig, etc.
everything was working great. but then i added the code for accelerating.
at frist try the robot was accelerating well, but at second try it didn't start moving at all. i removed the code and it still didn't move. it freezd. i had to remove the battery from the brick to turn it back on.
this is the code for moving forward

nSyncedMotors = synchBC;
nSyncedTurnRatio = 100;

motor[motorB] = abs(speed);
while ( (SensorValue(stikalol)!=1 & SensorValue(stikalod)!=1) & (abs(dolzinapoti)<dolzina) )
{
dolzinapoti = nMotorEncoder[motorB] * STRAITRATIO / 360;
nxtDisplayTextLine(3,"dolzina %3.0f",dolzinapoti);
}

i found out that if i remove the abs function in
motor[motorB] = abs(speed);
the robot is moving...

i have no idea what is wrong because the first code with abs was working in the beginning. probably is something with robotc.

hmmh...
- have you initialized speed before the first call?
- what happens if you wrote
int dummy;
dummy=abs(speed);
motor[motorB] = dummy;