tedster - 3:36 am on Mar 22, 2010 (gmt 0)
Well, I guess that answers one question - Google does take action based on the tag. A month does seem like a long time to reverse out of the error, though. I would suggest a Reconsideration Request, if you haven't already done so.
Unfortunately, Google's resources seem preoccupied these days. As many other threads here illustrate, lots of things seem slower than usual. On top of that, the canonical tag is relatively new and we really have little data about how long it "should" take to reverse the effects of an error.