Bruce - I've been using a variety of Mac's, with different OS's to access the site, for the past few years.
Latest setup is OS 10.3, on an iBook. Everything seems to work perfectly well, except that I don't see the "notify moderater" button that is supposed to be there??!?!
And yes, it sometimes looses track of the posts I've read, but that doesn't seem to be Mac-specific, judging by what the others have said.
What browser are you using to view the site? Might that be responsible for the window blanking? Try Safari - I likie it a hell of a lot more that IE or even Netscape!
I didn't spend nine years in Evil Graduate School to be called "Mr Irish", thank you!