Sometimes I do get redirected to the portal, that append from time to time as well (just append today again).
But the SSL case append pretty much at the same times but only replace the SSL certificate of this domain by using the worldspot's one.
My routers are installed with DD-WRT v24 SP1 (with the last update from July 27 2009) and I use a Mac Book Pro with Leopard. I've tried and face this issues with Safari, Firefox and Thunderbird while checking emails.
Hope that will help you to get this issue reproduced and identified,
Warm regards,
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Sebastien Grosjean - ZenCocoon