Awakening a dead thread, but wanted to share my experience in case it might help anyone. Tl;dr: if you have the "blocked motor" error and there are little pieces of broken black plastic on the bottom cover (as mentioned above), most likely the clips holding the magnet for the speed sensor (hall sensor) have broken, and the fix is to simply replace the motor pulley assembly.
Anyway, if the motor spins initially and then the cycle pauses (cycle light flashes), the motor DOES NOT need to be replaced (as I've seen recommended by other threads). There is a problem with the speed sensor (you will get a "blocked motor" error message if you put the washer into service mode. Instructions for entering service mode should be taped somewhere under the control access panel, or you can find it online).
MAKE SURE THE WASHER IS UNPLUGGED BEFORE ATTEMPTING ANY OF THE FOLLOWING
The quick check-- If you open the front cover and see little shards/broken black pieces of plastic on the bottom of the washer-- most likely the plastic clamps that hold the magnet for the hall sensor (speed sensor) have broken. Look in between the black impeller and the motor-- if you see a black ring stuck the the motor face, that's the magnet and it's not supposed to be there-- it should be held to the impeller with plastic clamps. Most likely some socks or other articles of clothing have fallen over the side of the tub when removing clothes, and those can get tangled in things causing damage.
If it is the magnet, you don't even need to remove the motor to repair-- order a new motor pulley assembly (about $35), remove the belt, locate and loosen the pulley set screw (1/8 hex drive), remove the pulley (and remove the old magnet if it's stuck to the motor), install new pulley, reinstall belt, and you're done. Follow the service guide to check proper belt tension (you should be able to deflect the belt only 1/2" with your thumb). You might need to loosen the bolts that hold the motor on to reinstall the belt and get it tensioned correctly. Also, the set screw may be very difficult to loosen. On my machine, I did need to remove the motor in order to get the set screw out because I had to heat the set screw with a torch to soften the thread locking compound (though you could use a lighter). I wasn't concerned about melting or damaging the plastic impeller because that whole assembly was getting replaced.
It is difficult but not impossible to remove the motor without removing the entire tub. I recommend placing a 2x4 and another inch or so of support material underneath the pulley before you begin loosening the motor bolts to hold the motor up-- the motor weighs about 20lbs, so it is very awkward handling it once the bolts start to come out.
It is also possible that the hall sensor has been damaged-- repeat the steps above (you will need to remove the motor) and the hall sensor easily unclips from the motor (the little green circuit board attached between the motor and pulley). If there isn't visible damage to the sensor, it's probably okay, but you can test it; however, you cannot test the hall sensor with a multimeter set to AC millivolts as the service manual suggests. You CAN test it easily if you have a DC power supply that reads current, or you can simply use a 9v battery with your multimeter in current mode. Simply connect the + supply to the blue lead, the - supply to the pink lead and set the supply to 10VDC. With the new pulley installed (magnet in place) rotate the motor and observe the current-- there should be 0 current for half the rotation, and about 20mA for the other half (hall sensor opening and closing as the magnetic field rotates). If you're using a battery, connect the positive and negative as above, but connect your multimeter in series with the battery + to the blue wire on the connector and select DC milliamps on your meter.
Hope this helps someone, as the clothes spilling over the side and damaging the speed sensor seems to be a common problem with this unit.