BRL,
Some services (applications can run as a service so they function even if no-one is logged in) cannot be stopped via Task Manager, but can be stopped using the Control Panel / Admin Tools / Services applet.
If they still don't stop, change the service to "disabled" and then reboot to stop it from starting.
To re-start, simply mark as Automatic / Manual as appropriate and Start the service.
It does look like it could be a firewall / AV problem.
Remember that Outlook uses different ports for email (pop3 110 / smtp 25) to those used by browsers for web traffic (http port 80, https port 443), so it's not so strange that email is OK.
Try running (briefly) with one or other (firewall / AV) disabled to see if you are still getting the same problems.
SD