How does MATLAB nprtool initialize a neural network?

I've been working with my own code for a pattern recognition network for some time now. I decided to try out the ANN toolbox from Matlab and ran into an error immediately. The stimulus for my network is nsamples (npatterns) by nelements. I have 179 different patterns and 3672 elements in each pattern.

When I load the data, I get an error saying the maximum variable size is exceeded. I've never run into this problem with my own networks. What is the ANN toolbox doing before it sets up and starts training the network?

Adam