OK OK - Enough...
Solution:
1) Enable MTP on Nexus 5 Device:
Goto Settings, Storage, (three dots in top right corner) Options - brings up "USB computer connection" - click that, Disable Camera PTP if it is enabled, ENABLE (check) Media device (MTP) - if it is already, uncheck it then recheck it. Let you computer find the ACER ADB again... IT's GOING TO BE OK... move on...
2) In device manager on Windows (I have win 7) - choose the Acer ADB device... it might temporarily recognize Nexus 5 and have a ! yellow warning on it until it installs the device driver and it incorrectly identifies as an ACER ADB device.. after it is done - select the acer ADB device, right click it, select UNINSTALL then *** this is key *** when uninstalling CHECK THE DELETE DRIVER check box also!
3) When its done uninstalling and deleting the Acer ADB driver - if it doesn't automatically just start working - unplug the phone and plug it back in - it will usually 99% of the time - just pick up the newly detected usb device and find it as a Nexus and download the appropriate driver really quick and whammo - open up the file manager or whatever default you setup...
Try that... big thing - DELETE the acer ADB driver when uninstalling... it will force it to look for a new driver...
Of course - you can also just install the android studio SDK and install all the packages for usb drivers...
This worked on my Nexus 5 with Android 5.0 (updated this week) as well as my old 4.4 Android.
Your Welcome
-GoZippy