Just to add to the above posts for anybody struggling to get their Nexus 4 recognized by Eclipse - ADT. In the past the device was recognized by Eclipse ADT without any issues!
I ran into the same problems as the original question. Every approach I tried wouldn't work...
Simple solution in the end
Go to Settings -> Storage -> USB Computer Condition (Menu option from Storage Screen)
Change from Media Device (MTP) to Camera (PTP)