This verse is the most over-used verse of Scripture that I have ever seen that doesn't prove anything that Protestants want it to...
I think the point protestants try to make is that they check things out in scripture. The New Testament as well. :-) I don't see many Catholics blowing the dust of the Bible checking to see if something the Pope said jives with the writings.
Because we know that it does. We don't have to second-guess the Holy Spirit working through the Pope, unlike our brothers who rely on their own intellect to decide for themselves what is Christian beliefs, not knowing for sure if their interpretation is God's meaning.
Regards