don't try to replace node that won't be accepted.

theano/sandbox/cuda/opt.py

@@ -54,6 +54,7 @@ class InputToGpuOptimizer(Optimizer):
                 try:
                     new_input = host_from_gpu(gpu_from_host(input))
 
+                    if new_input.type==input.type:
                         env.replace_validate(input, new_input, "To allow further optimisation to move Ops to gpu")
                 except Exception, e:
                     #as we currently only support float32, this can fail.