Thanks people. I can see from an internet search that this problem seems to affect an awful lot of people. Problem is that there are tons of different answers. I've removed one of my two anti-malware programs, and that seemed to help some.
From what I can see I may have a corrupted Winsock registry, but the fix from MS does not seem to work. Anyway, I plod on, and if I find anything definite, I'll let you know.