Continuous Safari error connecting to select servers

Hello---

For about a month (potentially longer, my memory isn't the best) I've had issues with Safari connecting to the server of a social networking site (tumblr)--however it's only every couple of pages and I get the typical white error message page. If I wait a few minutes (and sometimes longer or shorter) and refresh the page, it will connect. However it's not just a problem in Safari--the problem also occurs in Chrome (however the error message will say it "cannot connect to network").

I've tried multiple approaches (detailed here--https://discussions.apple.com/thread/4069569?start=0&tstart=0 and here--https://discussions.apple.com/docs/DOC-3681), but none have helped so far. However, in the process detailed in the first link I provided, when I put my computer into safe mode I had no problems (while the problem persisted in the guest account experiement, but instead of a error page, it was purely blank and wouldn't load).

I've reset Safari, changed DNS multiple times (currently set to the two DNS available in the second link), restarted the computer, etc, but nothing seems to help. The problem original came to my attention while I was at home over the winter holidays, but now I'm back at univeristy and the problem is continuing, disproving my hypothesis it might have been just a problem at my home. Any suggestions? I have VirusBarrier X6 installed that has some IP addresses blocked that were deemed troublesome--do you think if I unblocked them the problem would cease? I believe the VirusBarrier has been installed since roughly the time this problem started occuring... (Or is an update to Mountain Lion required?)

I've very eager to get this problem fixed, as running in safe mode all the time is not at all ideal nor would it make any sense. (I'm /very/ much a novice when it comes to computer related issues, so if there is something obviously wrong or something I obviously missed, please point it out.)

(I've had my MacbookPro 13" for about five months with no problems before that point.)

Safari-- 6.0.2

Mac OS X Lion 10.7.5