A PR5 site should get crawled daily by googlebot, and cached each crawl, so you should not be seeing a date older than say jan 18-19 on your cache. I am seeing a date of the 9th for it. I am also seeing that over half your indexed pages have no descriptions in the listings.
These may be signs of trouble, and if you did anything recently that you are not sure of, you may wish to correct that. i would especially check on new link partners to see if you may be linking out to someone you prolly should not be. You also seem to have a overabundance of footer links right on the front page which may be seen as "spammy" if reported by a competitor (a more and more common occurence perpetuated by lame
SEO's who cant rank their clients the right way).
I would suggest asking matt cutts if he would mind checking the site out and seeing what he says on his blog, or in an email. But not sure how fast that may be answered, if at all.