I have about 5 clients whose sites are hosted on our VPS who cannot access their sites from their office computers. DNS is fine and there doesnt seem to be anything wrong with the host - no downtime and bandwidth limits and size is ok.
Webmaster Tools also indicates nothing is wrong. I can access the site from several locations (office, home, friends place) but the clients cannot.
I am at a loss as to what could be causing this. Could this be an issue with their ISP?