Hi,
Sorry about the PR. Not all PR checkers are created equal. You need to use a reputable fake PR checker rather than a general one. seologs.com and sem-faq.com are my checkers of choice.
Even fake PR checkers can be fooled. Sometimes they pass a domain as valid, such as fakeprdomain.com, when the real PR is held by a domain such as fakeprdomain.com.mx If you get a green result, double check by typing: info:domaintobechecked into Google. If you see a result showing your exact URL without a redirect, the PR is probably valid.
There is no way to 100% guarantee valid PR but these methods are pretty solid. I employ them when compiling my lists.
Matt.