Yor example can be found in ESL texts, take a look for instance at:
????! - Daum ??
it was also discussed at yahoo answers, see
Grammar: Is this sentence gramatically correct? - Yahoo! Answers
And I think it was originally printed in Scientific American.
But I still do not know the answer, this very same construction can be found in song lyrics like:
"All you did was get me through
I owe every breath to you
Heart and soul unparalyzed
All you did was save my life"
(Our Lady Peace)
" All he did was tell me lies to try to woo me
After all the talk I guess he won the prize
He never meant to stay
How could be do it to me" (Kim Karnes)
However, the other construction, using "to", can also be found for example in
"The thing the sixties did was to show us the possibilities and the responsibility that we all had. It wasn't the answer. It just gave us a glimpse of the possibility." (John Lennon)
And the 'ing' construction:
"There was a little moment of silence then how
well I remember it! The schoolmaster broke the silence by adding : "Well ye know, lad, I think the greatest thing that Jesus Christ did was showing to a wicked world the sanctity o' motherhood." " (The light in the clearing; a tale of the north country in the time of Silas Wright - Bacheller)
So the doubt persists.
Could someone please shed some light on this subject?
Student or Learner