Hi, random cross-browser issues can be very tough to troubleshoot. Do you have a particular page on the site that has this issue? I didn’t see a map on the link you gave.
How many reloads does it take to see the issue?
One common problem is the map will appear to not load (or only partially draw) if it’s being displayed inside a container that’s initially hidden, like a tab control or hidden <div>. Check out the FAQ posting in the forum for info about that issue if you think it might be the cause.