I had that same problem the other day. The first day this was posted, I set my marker at work and everything was fine. I checked at home the next day and I couldn't see markers or the zoom bar. I was running WinME. Today, I just installed Win2000 and now I get an error and can't see the map at all.
Don't bother making fun of my OS or telling me I need to get this or that. I've been having huge computer problems for a while, so I've needed to take a few technological steps backward recently.
Anyway, I'll check from work again tomorrow and see if it's working there still.