idolw - 12:08 pm on Jul 21, 2012 (gmt 0)

I am seeing a weird behaviour for some of our old pages.

When we started the site we did everything manually for a few years. URLs for some important pages were written by hand. Then we set up a CMS which did URLs by certain rules. The old URLs were 301ed to new structure and everything was fine. Pages ranked very well.

The last year was a gradual decrease for the site but we did not have time to investigate too much (other projects) and now, when the damage is severe, we started evaluation.

What I see now, is the old pages lost most of their rankings (went from page1 to page 2-20) for multiple extremely competitive keywords. One reason may be links and not much work done in last 20-some months.
However, the weird part is that:
1. Old URLs rank anywhere between page 1 and page 20
2. Some old URLs are presented in the SERPs in an: Anchor text - SiteName.com format
3. Some old URLs are presented with their normal titles
4. Google Webmaster Tools show links to old URLs
5. Cached versions of old URLs show up-to-date content and current date (+/- 3 weeks)

Now, the questions are:
a/ why does Google link to old 301-ed URLs from SERPs?
b/ is there some technical problem?
c/ should we consider removing redirects and start using old URLs again in the hope for improvement in rankings?

Many thanks in advance