Hi Vitor,
I duplicated your app in VS 2008 RTM + Vista RTM Ultimate. I was unable to repro the strange access violation... but given that it happens when you click .pdf links inside the WPF browser control, it's likely an issue with PDF on your machine. The WPF Web browser, internally, is simply an instance of the same Trident object that IE uses. Thus, you can very likely repro this problem in Internet Explorer, and without WPF.
Some things to try:
Run your app on other machines, both XP and Vista if possible
Re-install Acrobat reader / WPF
Good Luck,
Matt
