[Q]Need help with Nexus 4 CyanogenMod 12 topic

I already install the CyanogemMod 12 on my nexus 4, it already installed for a past few weeks. And then some problems occur. The problem is when i connect my nexus 4 to PC via USB, it doesn't detected by my pc. It just detected as Other Devices -> 'Unknown Device'. I already try to change the port usb but it still give me same error. And then i try to go to Setting -> Storage -> USB computer connection, but it doesn't do anything. It just going back to storage. Usually after we click USB computer connection, it will go to some option like camera and mtp, but mine doesn't do anything. and i try to use ADB connect with developers debug mode and IP/TCP. it works, i can do 'adb reboot bootloader' but after that when i try to use 'fastboot oem unlock' it just 'waiting for device'. and when i use PdaNet, it can't detect my nexus 4. I hope some of you guys know about this problem and know the solution too.

Note : my nexus 4 just have some problem with soft keys (which i believe is hardware problem). I don't know if this is has some impact with my problem up there. and sorry for my bad english.