What do you mean by “not listed”? site:http://www.mydomain.com returns no results on Google?
(Btw, the PR you see on you G Toolbar is just a “static PR”, the real PR calculated behind the scenes all the time, what you see on the toolbar is a 3-4 month old record – G updates its “visible” PR each 3-4 months.)
Are you sure you don’t use any black hat seo? I mean black text on black background, redirects, cloaking pages?
Or you could check your link partners (your outbound links), maybe one of them is penalized so you have bad neighbourhood.
Hope this helps!