OK so I got those validity errors from the html tool at w3.org.
For this page
http://validator.w3.org/check?uri=ht...Brochures.html
Here's all the debugging output so maybe it'll be easier to find the errors:
http://validator.w3.org/check?uri=ht...00=1&verbose=1
Error 4 is that the head tag is closed but never opened. That's different than what I said, not nearly as fatal.
There's actually nothing wrong with the page. Just change META to meta and it will validate.
Is it possible that the tidy experiment coincided with an increase in competition? Maybe tidy is a lark and the problem is marketing?