There have been a few threads discussing problems with OmniWeb 5.7 sp not displaying content on pages until you do a refresh or click the content area and select all (this will then show you everything selectable, but not anything that isn't). This is possibly a problem in WebKit as some Safari users have reported similar issues.
However, if you have a cast-iron, 100% reproducible means of showing this then perhaps OmniGroup would be interested to see it?
Fwiw, the reduced , non-IE owa interface worked fine for me in 5.6 but I no longer use owa as my employer requires us to have a key fob for it, which I haven't bothered to request yet.