We've seen various people on this list blame the proprietary
driver for various problems before and it hasn't turned out to be the
issue. What proof do you have ?
That it doesn't happen for anybody who's not using proprietary crap.
And your #1 offender is another piece of proprietary software, the Flash
plugin (nspluginviewer is just a very small shell, its CPU usage is
definitely due to the plugins in it!), so if NVidia isn't the culprit, Flash
is and vice-versa. Neither is supported by us.