Hi Lucinda,
Yes, I have this problem on my mac too and still do if I use the Safari browser. I believe it is that Multichat is incompatible with Safari but I'm not sure as Multichat never did answer any of my many emails about the problem.

You will need to use Internet Explorer to participate in chat. That should sort it out for you so that you have a white screen and will be able to see everyone. If you still have problems next week using Explorer, let us know and we will see if anything else can be done.

Hope this helps!
Claire