I suppose that it all depends on your definition of choke.
To me a choke is Greg Norman shooting an 82 in the last round of the US Masters when leading, not dropping a bike during a race. Alternately if your definition is that he dropped the bike due to pushing to hard to stay in front of VR, then I assume yes he may have choked.
To me however he did anything but choke. He was doing what he (realistically) needed to do and that was to beat VR on the track to gain points back.
CS like most here does not expect VR to have issues or crash (he has had his one bad round per year), so what CS had to do was beat him on the track, and to do that he had to ride damn hard. Unfortunately when you ride these bikes to their limits eventually your number comes up and CS' did on Sunday.
In the sport, everyone crashes at times and rarely if ever would they truly be classed as a choke (and yes that does include VR 2006) as this is a sport that tends to produce the unexpected at times.
Don't forget that CS had gone a great number of race miles without a race crash (yes there was Laguna but that was nothing) and eventually it had to happen. Again though and to his credit he did remount and try to continue (which is becoming a common trait in todays MotoGP thankfully) so I do not think he chokes in any way.
Actually (and I think Roger alluded to this in another thread), his demeanor on return to the pits indicated a person who appeared comfortable with what happened (strangely actually). Whilst some may see that as confirmation of a choke, I actually see it as relief that he can now just race which is what he does best.
Oops sorry, did get away a bit.
Garry