Recently, I have been searching for a place to check PR that is consistent and accurate. I had been using one site to check PR of my sites, then one day to see if my PR had gone up, I checked the same site again and it returned a 0 PR
I checked around a couple other sites and my PR was either 0, "off" or what it had been for the last couple months.. Then I found ValidRank.com, which reported the PR I had expected to see and said that it was valid.. I checked it again on that site a few minutes later (just testing) and it gave me the same PR but called is "suspicious". I just don't know how/where to get an accurate PR for my sites and domains I look to buy that the owners claim to have PR...
Google toolbar will not show whether the PR is fake or not. For instance,
this site unoridian.com will show a PR5 on google toolbar, but... It's fake. The real owner of the PR5 is seizurerobots.com
Most online PR validators, including mine, can only verify the PR of a site if that site is cached by google. When a site isn't cached, there is no way to check whether it has a real PR or not. That's why it is considered Suspect.