CBA, yep I thought the same about Comodo but I've tried it in Clean PC mode and I still get the same thing. I have checked that WLM has permission for all POP3 and SMTP requests but still get the Socket Error.
I set up a Gmail account and tried WLM with that and it seems to be working fine. I'm now forwarding emails from Yahoo to Gmail to WLM which seems a bit ridiculous but it's working for now. Seems Yahoo are a bit tight with their POP server!
Twiggs thanks for the link, spotted it after I'd done all the above.
Thank you both for taking the time to help.