i didn't like it at first but once i got used to the multi window interface i've never looked back, its totally wonderful and beats all other browsers, the occasional problems of not being able to see a site properly sometimes is a very small price to pay.
check out these useful tools [westelcom.com] especially 04FE (file explorer) great for looking at cookies, cache and history an invaluable addition i think.
have you enabled cookies?? (F12 or file>preferences>privacy)
if you use the back button, you are pulling the page from the cache so you wouldn't be "logged on" on that page unless you hit refresh (F5) also applies to other pages you've visited... you can change preferences for cached documents
file>prefs>history and cache
the way my settings are i often have to hit refresh when revisiting a topic on wmw in order to view the latest additions to the thread.
- otherwise i'm stumped, love opera but am not of guru status :)