Does anyone have an answer to why "irrelevant" pages rank well or better than our "relevant" pages in our site?

Our site does very well in all aspects up till the last month or so... It is rich in key phrases in the title, yet kept to a minimum. The copy has the key phrases as well as the text links do...

Now, we drop to second page and some weird pages with mostly images and/or few words relating to the searched phrases. I actually had a small form page come up higher that us... it had half of the keyword phrases I searched.

Can anyone help me understand what's going on here or is Google experimenting in some way.

- Thanks