You have a really nice site. I think I see one of your "possible" BIG problems, but others will need to confirm my findings. I went to one of your pages randomly and cut and pasted a small snippet of text from one of the products into google with quotes around it, just like this:
"Fun and fanciful, arty and graceful, our chandelier and strand"

There are a couple of sites that have the exact same text in them and you might be getting penalized for duplicate content. Granted, one of the sites I saw was a social bookmarking site, but there was another site that wasn't that looked like the same kind of store as yours. You are in a competitive niche which could have an effect on how hard you have to work, but you got decent page rank so your backlinking efforts looks to have been getting noticed with regards to passing strength.
I randomly went to another page and noticed that you do not use Header tags anywhere, even on the home page.
The domain name has been registered a while, but how new is the content? If it's new, than that could also be a problem and you may have to wait a little longer.
Are you analyzing any Google websmastertools information? That should tell you quite a bit.
Last thing...the content on the page is very light. Not a whole lot of text, but I am not sure that matters.
I checked and saw that your domain has not been flagged on any blacklists, so is there anything else you can tell us about the site or what other seo stuff you've been doing?
How much traffic are you getting today? What % is from organic traffic?
Were you affected by panda or penguin updates negatively, and if so, which one? That will tell you a lot.

This issue may be due to copied content, and on page parameters not set properly. If duplicate content is the issue please rewrite the whole content and make it unique and start SEO again. This will give a great effect