I’ve experienced something like this before, not a hang but freeze for a long time, when the internet settings in the location document are set wrong
David Vasta —->
Sadly Lotus Notes 6.0 is not the Internet Client it should be. This of course upsets most people. You will in fact need to check your location settings. Make sure you can browse the web from Lotus Notes. Make sure you are using a browser that is able to access the web from inside Lotus Notes inside you office. Once you get that working you should be able to open HTML emails.
If it is possible I would recommend upgrading to a more current version 6.5.1, 7.0.2 are both better clients than 6.0