In r56207 (and many previous Nightlies) the Dutch T-Mobile site, www.t-mobile.nl doesn't display. There is only the background and several (unimportant) hidden elements. There are several Javascript TypeErrors, which are probably the cause.
I cannot reproduce this with r56652 nightly on Mac OS X 10.6 (64-bit). Could you attach a test case? Does this happen when you log in as guest, or in a different user account? Note that plug-ins are completely broken in most recent nightly builds, so central content doesn't appear on this site. This is bug 36966, which will be fixed in next nightly build.