While farting around with my other issue this morning, I slapped the new CNUT 4.10 on my laptop. Anyway, that didn't help that issue, but later when I went to update a directly connected "new-in-box" 450 SM from 13.2.1 to 14.2 (or any version in between that I tried), it spit back some java error saying it couldn't open a socket for 5x_cat120.img to transfer or some-such.
Reverting back down to 4.9.18 has resolved the issue. Sorry I don't have the original error message.
We are aware of this issue. As a workaround, you can use CNUT 4.9.18 to get up to a 14.x release and then continue using CNUT 4.10 for further upgrades.