I just tested this problem and I see the same result. Unfortunately I can't help you there since I'm not that familiar with the code.Maybe Jan has a solution.
I cannot help here, sorry. I don't see anything obvious or windows-version-depending within the WebKit sources, either.
Does it work on some more recent versions of Windows? Cheers, Jan -- Trojitá, a fast Qt IMAP e-mail client -- http://trojita.flaska.net/
