Firewall blocking internet?

Recently I've had problems accessing the internet and found that it can be fixed by setting my firewall from "Set access for specific services..." to "Allow all incoming connections." The connection is then made, and I can once again put the firewall up. I've repeated the problem and solution in several different locations, all of which were allowing internet to other computers and had allowed me internet fine previously. I also made sure my computer was up to date and still experienced it.

It just keeps happening! Sometimes when the computer wakes from sleep, sometimes in the middle of a session, I'll suddenly lose the internet and have to "Allow all" again. Naturally it's annoying to have to do this several times a day, and I don't want to just take down my firewall entirely.

This started happening just after my computer came back from repairs (they replaced the screen, disc drive, and trackpad). I can't think of why this would affect my firewall settings or network connections though.

Any ideas why it could be happening or how I can fix it? Please help.