TheMadScientist - 2:41 pm on May 5, 2010 (gmt 0)
I feel that would be unlikely to be a serious issue here unless for example the site had changed from www to non-www with the relaunch and the www now produces an error.
Except that using no / invokes a double redirect, which is advised against and, I think, those have been known to cause issues with link weight passing to the final landing page. It should not cause issues with all pages though, AFAIK.
Intra-domain it should be fine to even redirect http://example.com/ to http://example.com/page-name.html, even though IMO it's not usually the best course of action, and as long as there is only one redirect, it should transfer all (most of the) weight just fine.
The best reason I can think of outside of a Google issue is a spidering issue. I'd start viewing source code and double checking those robots meta tags, even though it looks like you already have.
Out of sheer curiosity, do you run AdSense and if so, how many blocks of ads do you have on each page?
If the issue is not technical, could you describe the scope of the redesign... Did page titles and content change too? Were site-wide backlinks added anywhere in the footer or anything? How much and what changed?