Huge PR drop

[manzan]

We have had a page rank of 6 for our home page for the last two years. The site has about 1200 informational pages. The other pages had ranks between 2 - 5.

Suddenly, I noticed after Christmas that my home page rank has dropped to 1.

About 2 months back I changed all the dynamic pages to static ones and added 301 redirects to the old dynamic pages. The new static pages have a blank PR.

When I search for specific key words, the relevant pages do not appear in the first 20 pages. When I add the site name (which is not a common word) in the search, the results appear in page 10 or so (the dynamic page shows up as a 'supplemental result' and the new static page shows up a few rows later). All the pages that link to my site show up earlier in the first 10 pages.

What could have caused this huge PR drop?
Does this sound like a temporary problem or could it be some kind of penalty?

My site is a genuine content site and I am not trying any funny stuff - just following basic optimization guidelines.

Thanks.