| 5:37 pm on Apr 27, 2009 (gmt 0)|
The Not Found report is for your information, it's not telling you those pages "should be" on your site or that a ranking problem is being caused.
However, it is possible that there are backlinks somewhere that point ot those urls. Have you checked that? You may be missing some PR power by not serving at least some content at that url, even a 301 redirect.
| 7:03 pm on Apr 27, 2009 (gmt 0)|
I've recently seen a similar thing, where old URLs reappeared in the list.
Even more bizarrely, old URLs that no longer exist were also being reported as being backlinks to pages that no longer exist.
It all cleared up after a few weeks.
| 7:22 pm on Apr 27, 2009 (gmt 0)|
I found "The Not Found report" to be very useful on one occasion when it came up with a missing page that should not have been missing. I'd goofed up and missed recreating it when I did a major overhaul/redesign of the site.
| 3:29 am on Apr 28, 2009 (gmt 0)|
I have similar issues listed in my WMT and had started a thread about a month.
These old pages keeps appearing and disappearing in my WMT even when none of them exist with most of them being 301 redirected to new locations.
| 7:28 pm on Apr 28, 2009 (gmt 0)|
It takes a while for 301 redirects to be reconciled; they'll pop up occasionally seemingly forever.
I believe that Google has some processes to 'clean house' a few times per year - and they briefly pop up then.