Where some noticed their PageRank drop from a number to zero but not lose any traffic at all.
Adam Lasnik, of Google, came into the WebmasterWorld thread yesterday in message number 3326575 and said they will look into it.
If you've seen your PR adjusted to a non-zero number OR you've lost significant traffic, this thread does not really apply to you.
If, however, your PR has dropped to zero AND you've not seen any significant loss in traffic from Google, rest assured that this is most likely a PR-reporting (PR on Toolbar) error; while admittedly alarming at first site, it's nothing to worry about. The tail does not wag the dog in these circumstances :)
With that said, I'll be chatting with some colleagues again today to hash out what might be occurring, and I'll report back here with any news.
Have a good week everyone.
I will keep you updated on any updates from Adam over the course of the week.
Forum discussion continued at WebmasterWorld.