I tried to update my DT25 112 to firmware version 2.00 last night and had problems. I thought I'd post here in case anyone else has a similar experience.
I bought a good quality USB - MIDI cable for this purpose, having read reviews of cheap cables on Amazon that often said they caused problems. I have the Monkey (and HD500X) software installed on my Windows 8.1 laptop, and it seemed to install the drivers for the MIDI cable without any problems as soon as I plugged it into the USB port. However, I couldn't get the Monkey to recognise my amp until I had rebooted the laptop, so that was the first gotcha.
On the subject of the cables, I did put the MIDI IN cable into the Output socket of the DT25, and MIDI OUT to the Input socket. No issues with that.
Having rebooted, the Monkey recognised my amp, told me that it was running firmware v. 1.00 and that 2.00 was available. so I told it to upgrade. It seemed to go through the whole process alright (downloaded the new firmware, installed on the amp, reinitialised the amp) but then told me it had failed due to an unknown error (always helpful, thanks developers!). However, when I rebooted everything and reconnected, it reported that the amp was on version 2.00 so I thought it was ok.
Then I plugged in my guitar...
Nothing. Not a sausage. Just a speaker crackle when I turned the amp on. Switches unresponsive (e.g. amp selection), no sound from the guitar either directly or via my HD500X. I tried rebooting everything, I tried doing the factory reset on the amp, to no avail. Then I tried to reapply the upgrade and to roll back to version 1.00 in the monkey software, but that didn't work.
Eventually I hauled my amp upstairs and plugged it into my desktop, which is on Windows 7. Happily, that worked fine and I was able to roll back to version 1.00, and my amp works again. Phew!
I don't even know why I wanted to upgrade, except that the upgrade is recommended by Line 6. If you have a pod (which I do), it doesn't give you any new sounds - it just means that you can also access the 30 amps without the pod. Great if you don't have a pod, no doubt. However, the other issue is that there is no software for me to actually make those settings on my amp - they only have software available for iOS, and we aren't all Apple fanboys, Line 6!
So I'm going to stick with version 1.00 of the firmware. I decided to post this in case anyone else encounters the same problems, or to forewarn anyone wanting to upgrade from a Windows 8 / 8.1 PC that they may run into problems. For me, there are two essential lessons learned here:
1) Be careful about upgrading from a Windows 8 / 8.1 PC unless you're sure that your MIDI drivers are 100% compatible
2) Don't bother with the upgrade unless you have an iDevice or you have MIDI control software on your PC and are familiar with its use.
Finally, I love the amp but I have to say that this experience was not good, and wasted a lot of potential guitar time! :(