Something is blocking scrapebox. In a nut shell whats happening is your Anti-virus/firewall or maybe even malware checker sees Scrapebox start up and all is good, it sees it connect to the internet like a normal program, all good. Then all of a sudden after like 500 connections it says, this isn't a normal program, its probably a virus, as viruses act like that, but it doesn't fit a definition file so it just blocks it.
When you close down the program and reopen all is well again, untill you trigger the ban by hitting 500ish successive connections. The amount of connections is relative, but if you look thru your a/v and firewall you will see a rule about scrapebox, you need to delete that and add a rule for full allow access.
I have watch as this happened. Installed McAfee and turned notifications on and hit go in Scrapebox, hit the 400 connectionish mark and boom, all failed just as the popup went off from McAfee saying it had blocked scrapebox.
Find the rule, nuke it and add a full allow rule and you will be golden. Its possible it could even be the firewall in your router, but typically its software on your pc.