Using OS 10.8.2, Safari 6.0.2, NIS 5.4.1, NortonInternetSecurityBF plug-in 1.4.0f6, Adobe Acrobat NPAPI Plug-in, Version 11.0.02.
When I click on a link for a pdf file, it starts to open in a new tab and then stops (the blue loading bar goes part way and then stops). It says "Loading xx KB/yy KB". Hitting reload doesn't work. But if I click the same link a second time it usually opens right away. If I clck another link the same thing happens for that pdf. I know it's the NIS plug-in causing it because if I turn it off, the problem goes away. It's the only extension listed on the Extensions tab of preferences.