incrediBILL - 1:23 pm on Jul 19, 2010 (gmt 0) [edited by: incrediBILL at 1:24 pm (utc) on Jul 19, 2010]
The only significant change we made was the page names. ... We also had all the content redone by a professional copywriter!
You can't do those things and expect to retain your original ranking.
Even if you 301 redirect from the old page to the new page, it will take time for Google to reindex and adjust the toolbar PR for the new pages, you may have PR but just can't see it. If the pages don't show up in the index where they previously did, that's a clue your new page has no juice, possibly since a copywriter redid your content so the content that was ranking very well is now gone.
IMO, too many variables have changed, you started over from scratch and now it sounds like Google has possibly reset your site back to zero.
You can wait on the current site to rank if you have patience, and possibly months (years), to wait while the new site gets the same ranking, if ever.
Reloading the previous website sounds like your only option to quickly regain what you had.
Seriously, I would probably start over and try upgrading one thing at a time. First, apply a new layout on the old site using the old page names and content to see if that regains your rankings. Second, see what happens with the new content by slowly replacing some of the better ranking old content. Lastly, I'd probably just leave the page names as-is, I've changed thousands at a time before and it's a big mess and takes patience to wait for ranking to update.
Also, what about the meta tags, did you also change your meta keywords and descriptions?
Not that they matter as much, but it all ads up in the end.
[edited by: incrediBILL at 1:24 pm (utc) on Jul 19, 2010]