Welcome to the Q&A Forum

I would argue these topics are easier to build links for because they are so niche and therefore less competitive, so perhaps you should go back to basics and try some or all of the following:

Niche directories - i know directories are old hat and outdated, but if you could get a few links from "eco" sites (toxic waste removal) or indeed government sites such as town councils etc then you will get some benefit. Don't forget it is worth linking out to authority sites too i.e. if you link to the local council site on how to get rid of toxic waste safely then then your link neighbourhood improves.

Niche publications - If you can place articles in these sites with contextual links then you're on to a winner. Case studies and how to guides are always welcome material.

How to guides - Especially when it comes to plumbers, boilers etc. I worked with a plumbing company before and suggested they post how to guides on everything from fitting a tap to what questions to ask your plumber about a new boiler etc. The push back here is often that "if we tell them how to do it then they won't get us to do it", but would you really try and fit a boiler yourself if you had the instructions? Try http://www.e-zine-list.com/index.shtml for a list of niche pubs

Become the expert - sites like Yahoo Answers are awash with people looking for answers on various topics so if your client can put in a little time each day to answer questions they could become recognised as the go to guy on their subject.

Hi Ben.

Have you checked to see the articles themselves have been indexed by Google? In other words using the site:search or the article title in ""?

If they are indexed and you are looking for the links themselves i.e. link: then it is probably because Google doesn't show everything, just a sample of links pointing to your site.

If you use Open Site Explorer or MajesticSEO you will get more reliable link figures, but again you should bear in mind that OSE and MSEO don't contain the entire web so may not have picked the links up yet either.

I have a bastard of a problem... Google Analytics is incorrectly tracking PPC traffic as SEO which is screwing up all my reporting .

I don't care for rankings, I care for actual SEO traffic and I can't be sure that what i am seeing is correct which is driving me nuts.

Any ideas?

To keep your pages and avoid the duplicate content issues i would suggest expanding your product description e.g. 
Dell Color Compatible 3130CN －Magenda with chip 
Dell Color Compatible 3130CN －Black with chip

...those are your produce titles, which is fine, but they are also the in page product descriptions and there is only one word different.

Now the reality... you have over 20K pages indexed so the above approach may not be so practical unless you have a bit of cash to throw at a mechanical turk project that gets all your product descriptions rewritten.

You really ought to introduce something like Disqus that lets people comment on products which in turn would generate a load of unique content, but this would take a long time.

If I was you I would consolidate products like this into a single page with a comprehensive product description and then put a canonical tag on each of the individual product pages so you can still keep them separate, but for SEO purposes you are telling the search engines to pick up one great pages and not loads of poor pages with no unique content.

Finding Link Opportunities With Advanced Search Queries | Distilled blog http://ow.ly/1swIgW

White Hat SEO: It F@$#ing Works | SEOmoz http://ow.ly/4xeL4

The Evolution of Google's Rankings http://ow.ly/4fhi3

This may be a silly question, but have you got Google Webmaster tools installed? That will show you the source of the errors.

If your site is on IIS then you should also use the awesome IIS SEO toolkit provided by Microsoft for free.

I think it's the SEOMoz crawler, but what I have found is that the error reports are limited here whereas GWT is much bigger and shows the links leading to the error. My guess is that SEOMoz limit the number of crawl errors they show due to limitations set on their crawler i.e. while their crawl is comprehensive, it's not going to capture what Google does.