Nexus 4 problems connecting usb mtp
I have Windows 8.1 and I had the same problem, PTP working, MTP not. I was following the steps suggested in this page but it wasn't doing the job, until I made some previous steps, and slightly changed the last part. Summarising what I did is:


Connect your device.
Unistall ALL the drivers from the Device Manager, be sure to go in "View"->"Show hidden devices" and then check that all of the following are unistalled:

a) Android Devices

b) Other devices

c) Portable interfaces
Now disconnect your device.
Check the PTP mode and connect your device. Wait for the drivers to be installed.
Without disconnecting check the MTP mode on your device and wait the drivers to be installed again.


Now it should WORK!! At least it did it for me ;)