"the loop that contains 'RobotDriove' is not running fast enough"

[hello world!]

i tried getting a four motor tank drive program working. The first thing I tried was to replace the open two motor drive with a four motor drive. i tried testing this and i got an error saying "the loop that contians robotdrive is not running fast enough" along with other things that it says I should try to fix the problem. the strange thing was that it didn't just make my drive motors stop working, i couldn't even get my other motors to work either... so i tried replacing the four motor tank drive with a two motor drive again and it gave me the same message.

What does that error message mean and how can I fix the problem?

What's a good way to get a four motor tank drive to work? (I have four motors because we're dealing with a two speed transmission)