I just had the same type of problem with a site in my bookmark section. It did NOT affect all of my bookmarks.
One day I could access the site, the next day no way! After spending hours on the phone with a technician, he came to the conclusion the bookmark had gone bad. I trashed the bad one, then re-bookmarked the site after pulling it up manually. Voila!! No more problems. Maybe this will work for you.
Tom
P.S. I had no idea a "bookmark" could go bad! Maybe if I were to give it more love, quality time and attention, it would continue on the right path!