Login, Session, redirection, failure...

[eluser]LuckyFella73[/eluser]
Did you check the cookie setting while testing on the 4 PCs?
Sounds strange that your application runs on Windows PC 4)
and not on PC 1) using the same browser. But you never know ..

Did you set the cookie_domain ?

Code:

$config['cookie_domain']    = ".your-domain.com";