Same problem here!
My G2 is recently updated to 4.4.2.
I have tried on several computers, different ports and no help.
On the first connection to a PC not connected before windows reports "USB device not recognized" problem.
After that every time I connect the phone to the same computer the phone itself only recognizes that it is using USB charging mode, it does not recognize the computer connection (known by the USB icon on android system tray) even with "Ask upon connection option checked".
Even when I manualy change the Android mode in Settings --> PC Connection from MTP to PTP or even LG software, nothing happens.
Definitely there seems to be a problem with the phone, but I don't believe it's a software but a firmware problem.
Please help if anyone knows what to do.