Banned Pages?

Hi,
new guy here...I posted this over at the google forum, but after looking around a bit this may be the proper place..

My problem is this.

My site milodon.com is fine with a rank of 6 in google for it's prime keyword...but
milodon.com/valves/megaflow-valves.asp this page was up on page 1 for racing vales and now it's nowhere to be found. It's a big page, would that be enough to get it banned?


the page shows as indexed in my google account...but not when you directly search for it? I'm at a loss

Any help or new ideas are appreciated

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it is ok now in 2008