First, you should upgrade to the latest version of Vectorworks. 10.1 has bugs.
Second, make sure you have enough RAM (the more the merrier with this application).
Third, check to make sure you have upgraded both the drivers and the firmware on the plotter. If the plotter is on a network, you have to disconnect it from the network, and hook it up to one machine with a parallel cable in order to upgrade the firmware. Then connect it back to the network.
I have the PS version of this plotter and only have trouble with time it takes in Postscript mode. Non-postscript works right away.