I cannot use chat. The only way I can PM someone is if I go and search for a member first. I cannot look at member profiles and choose to send them a PM (possibly chat there too?). If I go to lok at a profile, I basically get told I don't have the right access to do that. This issue happens for me on the following combinations:
Mac, OSX Lion, Safari
Mac, OSX Lion, Firefox
Mac, OSX Lion, Google Chrome
iPad, iOS 5, Safari
I think that it could be browser related (cookies or JavaScript not enabled or something) but if it seems widespread with members, it might be a setting within the forum software itself instead if a combination of OS/browsers on the member side.