mobile

Hello,
this is my first post here.
I recently rooted my LG G2 AT&T (D800). It was running D80020y.
Also recently AT&T offered the update to Lollipop (D80030f). I did not accept the update but ATT pushed it anyway when I rebooted the phone.
After that the phone would not boot, it would just go into recovery mode. I have TWRP v2.8.5.1.

Many of the posts addressing situations like this require installing the D800 drivers in computer, and installing adb.
I am trying to solve this problem from a PC running Windows 7 Pro. The PC is not able to see the device.
"adb devices" returns nothing. Not an errror, but an empty list.

When I connect the G2 to the PC, the (windows) device manager lists it twice:
1) Under "portable devices there is an entry "LG-D800", and there I get "this device is working properly", and it uses Microsoft drivers under C:\windows\system32\ and under C:\windows\system32\DRIVERS.
2) Under "Other Devices" there is an entry like before, "LG-D800", with an error sign. When I open that entry I get:
"The drivers for this device are not installed. (Code 28)
There is no driver selected for the device information set or element.
To find a driver for this device, click Update Driver."

Even if I click "update driver" and navigate to the installed LG drivers they won't load. The PC says that nothing was found.

I've tried this also on Windows 8.1 with the same results.

However, with the phone plugged into the PC I can see its contents with Windows Explorer, and I can copy files into it.
I just can't run adb or fastboot.

Of course, I am not able to change to "USB debugging" mode because I can't boot the phone. For the same reason I can change to PTP mode.

So the larger question is how to get my phone back to booting, and I've seen references to that in xda-developers, but all of them use adb,
and for that I need the PC to be able to see my G2.

Thanks!

Asttor