Hi,
did you change something in your model? Maybe an output layer for finetuning to your specific problem?
I suppose the size mismatch error could be located in another layer besides the input layer.
This code sample works fine for me:
model = vgg16_bn()
x = torch.FloatTensor((10, 3, 224, 224))
x = Variable(x, volatile=True)
out = model(x)

Could you give a working code snipped throwing your error?