I created a Radio Button group with two buttons
Group name is CurrentData
One button name is "Q&A" and one is "SESAME" (without quotes)

Just imported 6000 Q&A records and want to Mass Update all these records to have "Q&A" value selected.

Did Mass Update in CurrentData element:
CurrentData = "Q&A"

Run Mass Update on 6000 records, but when all done, both choices are still inactive.

What did I forget to do?

If your button name is "Q&A" then your label definition is probably "Q&&A".  Change the Mass Update spec to match the label definition, not the name.

CurrentData = "Q&&A" 

Wow..two identical responses in less than one half hour.  Support is terrific.

You were both correct, when I changed to "Q&&A" it worked.  Thanksalot.

But now I notice when i single step through the records using the mouse on navigation arrows, some records flicker on "Sesame" before settling on "Q&A"  There is no programming that affects the Radio Group, and value does settle on "Q&A". 

Quickly clicking makes it appear that some records have value of "Sesame", but really have "Q&A"  Is this normal, do I have to live with this?

Yes, initial Value is "Sesame".  But I need to keep that for new records.  Does that mean I should use programming to set CurrentData if @NEW instead of using Initial value?