I have the same problem on a store and no-one in this forum knows the answer to the question or at least I haven't found any specific nail downs to the issue. One area said to use the access key not the developers key. I have't tried that yet since you have to get an access key from ups and they recommend testing with a developers key first. Other area say to change something but do not tell were. guess we can search in every file in the module and change it to see it it does anything.
ceil($order->info['subtotal'])
to
True, you made it into a function, add global $order; as the first line in that function.
but they didn't say how to change that.
I would guess it would need to be ceil(global $order->info['subtotal'])
Lots of luck finding a specific answer to the issue. Good Luck getting UPS to even verify that the key has been activated