Yes, very repeatable. Just checked both computers with Rhino.
Computer 1. Windows 7, AMD Radeon HD3770 graphics, AMD driver 126.96.36.199 8/30/2013
Rhino Version 5 SR8 64-bit (5.8.40224.15545, 2/24/2014)
Click on Properties under File
Properties pop-up menu opens with Mesh highlighted
Move cursor over pop-up menu and my name and date appear in the area with the mesh properties. Can not modify any mesh parameters.
Move cursor to Units and click - now okay.
Move cursor to Mesh and click - now okay.
Computer 2 Windows 8.1, NVIDIA GeForce GT 740M driver NVIDIA 188.8.131.5289, 3/8/2014; Intel HD Graphics 4600 Driver Intel 10.18.10.3379 12/18/2013
Behaves the same as Computer 1 except Grid is highlighted rather than Mesh when Properties pop-up menu opens.
This has been happening for several years with beta versions of Rhino 5. In the past Units was highlighted when opening the Properties menu.
My recollection is it also happened with Rhino 4 but am not certain.
I’ve become used to it so it’s a minor annoyance for me, not a major problem. But it was alarming the first several times it happened.