Sudden occurrence of 10060 error

[Foxfan100]

Win XP SP3, Avast 4.8.1356 Home, VPS 090926-1, email client Thunderbird 2.0.0.23

I'm using a Belkin N1 router (wired mode) and connecting to the actual SMTP address (212.100 etc) of my ISP. This has worked perfectly until today, when I have suddenly started getting a 10060 connect error. Nothing has changed at all in my setup. If I terminate the Avast Internet mail provider, my emails get sent first time.

However, I have another PC (exactly the same setup as above but a laptop) which is connected wirelessly to the Belkin router, which will send emails perfectly when the Mail provider is running!

I really cannot see why this should be. I don't really want to have to turn off the Mail provider every time I want to send something, and if possible I'd like to stick with Avast as I've used it for several years without a problem.

Help, please!

[DavidR]

Well the error number = A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond.

You don't say if this ISP/email server user SSL/TLS (securer encrypted) as avast can't deal with secure communication ?

Have (or did) you another AV installed in this system, if so what was it and how did you get rid of it ?

What is your firewall ?
Does it allow ashMaiSv.exe internet access ?
- If it does delete the entry for it and try sending again, this should force the firewall to ask permission again. Though if the firewall was blocking it should also block ashMaiSv.exe for inbound email.