I remember a few times when the NRA gave high grades to politicians who have anti-gun pasts.  Does this still happen?

Yes, their ratings are crap.

Hmm, I was not aware of this and have often used NRA ratings as a guide before voting. Anyone have specific examples?

2006, Jeanine Pirro running for NY AG was given a C.  She deserved an F as for years she used her office as Westchester DA as a soapbox for gun control.  2008, Sandy Treadwell was giving an A in his Congressional bid while his record as NY GOP chief at best suggested indifference to the issue.  Plus he lied in a campaign mailer.  From what I've seen, about 25% to 35% of their ratings are off, either too pro or too anti.  In the NY-23 special Congressional election Dede Scozzafava was given an A, but that is a bit generous as while she voted with us against gun control, I can't recall her ever promoting pro-gun bills.

To be fair I don't believe all of this is deliberate.  I do not think they spend enough time looking at incumbent records and I do not believe they research challengers enough to make informed decisions.  Most of their endorsements go to incumbents and the bulk of them don't really need them.  I suspect that is because they just don't have the ability to use their resources in the most effective manner.

After looking at some scores of politicians I know well, I found their scores were very acurate.  I guess a few slipups will happen given that there must be over 1000 people to score nationwide.  Are there anymore examples of bad scores?

As I said I see about 25-35% of their grades are off every cycle, either too pro or too anti.  One Assemblyman votes against us everytime and has a press release touting gun control on his website gets a B while another who votes with us everytime and sponsors good bills get a ?.  One former Assemblyman got As and endorsements when he voted against us 50-60% of the time.  I gave him the C he deserved an took him out in a primary.  The list goes on.

I'm trying to find Obama's score.

I give him an F.  He is clearly anti-gun and also lies about it, so I think the NRA should give a special mark to people who want to do a gun grab but who lie in order to get votes.
F* or something like that.

   How can one be too Pro? Please elaborate....

I think he means that the NRA's grade is erroneously shifted in either the "pro" or "anti" direction.

For example, if a particular candidate should have a C rating, the NRA's rating would be too "pro" if it gave this candidate a B rating or too "anti" if it gave this candidate a D rating.

Yes.