I had this issue repeatedly myself, and just plain could not resolve it in what I would consider a normal way.
2 separate systems
1 With a Razor mouse, 1 without - so I do not consider that a factor (especially as I reset the polling rate to 125).

What it turned out my issue was is something to do with the 1155 / Sandy Bridge chipset. Now, while I did manage a work-around (the system works just fine once the firmware is upgraded).

I ended up having to make my own interface cable so I could connect to the aquaero 5 LT from my laptop with a standard USB port. There the firmware upgrade worked flawlessly the first try.

Now, I noticed that the actual point where it fails, is right during the reset portion of the upgrade - ie: The download happens, there is a short disconnect and then reconnect of the Aquaero from communications / the software (you can see it lose connection, and then restore it). On my 2 systems above, at this point it would just plain hang, and not finish the process. With the laptop connection it managed to continue on without a problem. So - there must be something different with an 1155 system (or at least an ASUS MB and 1155) and how it is resetting the USB on a disconnect / reconnect of the device. [ hopefully something here will be useful to others ].