No browser connection

[#1]

Firefox and Chrome on my laptop work fine. No issues.

On my desktop recently, for no apparent reason, all browsers fail, Thunderbird can receive but not send and Mailwasher works, again, with no issues.

Amongst the errors I'm seeing are:

PR_END_OF_FILE_ERROR
ERR_CONNECTION_RESET
PR_CONNECT_RESET_ERROR

Anyone got any suggestions for what the cause might be?

[#2]

It's taken many hours, but I found the solution: uninstall cFosSpeed (LanMan) and its driver! Absolutely evil!!