Duplicate homepage issues - Can anyone advise?

Hi I'm having trouble with duplicate content and I can't fathom what is wrong.

For my main keyphrase I used to rank on page 4 in Google, then for a few weeks I would randomly drop out completely, then reappear a week later back on page 4. This would happen for a month or so then 2 weeks ago I disappeared again never to return. My individual pages are ranking better than ever but the homepage is gone.

In it's place, I have discovered is a different version of my homepage. This -

Psycholocrazy | How to quit your job, find your passion and live life ...
http://www.psycholocrazy.com/page/2 Share 31 Oct 2012 – Do you ever have those days when you just cannot be bothered to do anything? Well I'm currently having one of those weeks and it's not ...

When it should be this -

Psycholocrazy | How to quit your job, find your passion and live life ...
http://www.psycholocrazy.com/ Share 3 days ago – Hi I'm Jamie and this is the blog to help you quit your job, find your passion and live life on your own terms. Stop doing what you hate and go ...

Notice the correct homepage url and my correct site description.

What I have done -

1. I have All in one seo plugin and I have no indexed my categories and tags and I have canonical url's checked.
2. I have submitted both www and non www to webmaster tools.
3. I have very reputable high PR websites (3-7) giving me backlinks (keyphrase variation) and no black hat SEO whatsoever.
4. My site is almost 6 months old and it was behaving fine until about 4-6 weeks ago.

To summerise -

Can anyone give me any ideas why Google is offering up 'page 2' as my homepage and stealing a snippet from a random post for the meta description?

Thanks for reading.