Neural Network GPU training with output weights fails with "No method 'subsref' "

When training a NN I would like to use output weights (between 0 and 1), but I get the following error :

No method 'subsref' with matching signature found for class 'gpuArray'

My function does the following :

% get the gpuDevice
% load data
% change 'tansig' transferFcn to 'elliotsig'
for i=1:net.numLayers
  if strcmp(net.layers{i}.transferFcn,'tansig')
    net.layers{i}.transferFcn = 'elliotsig';
  end
end
% I had to alter processFcns to avoid the following errors :
% Input processing function REMOVECONSTANTROWS is not supported with GPU.
net.input.processFcns = {'mapminmax'};
net.output.processFcns = {'mapminmax'};
% convert data to GPU data with the nndata2gpu function

% Then train
net2 = train(net2, x, t, [], [], wtsOutG);

The error returned is :

No method 'subsref' with matching signature found for class 'gpuArray'

[Aditya Patil]

Can you provide a sample code snippet that creates the error? I am unable to reproduce to error with the given code, hence it might be possible that the issue lies in rest of the code.