I noticed with the 0.23 update, and corresponding KAS update, I can no longer grab stock parts that were already attached to ships/structures. When I right-click, nothing happens. KAS parts do not exhibit this problem.
If I have a stock part in a storage container I can grab it and place it normally, then even grab it again. However parts that were already attached before upgrading cannot be.

The parts I've tried to interact with are the two lights, the 4-way RCS thruster, the rockomax 24-77, and the fixed solar panel.

This includes parts I placed via KAS under 0.22.

Cleaning issues not related to the 0.5 version of KAS (KAS Grab/Storage is removed and replaced by KIS).

I figured out the issue by comparing parts that work with those that don't.

I had to set the 'isEnabled' property to 'True' on each part that didn't work (which was hundreds) in the save file. That restored functionality to the broken parts.
Not sure if that property was just ignored before or not.

            MODULE
            {
                name = KASModuleGrab
                isEnabled = False <--- change this to 'True'
                grabbed = False
                evaHolderVesselName = 
                ....more stuff....
            }