Nameservers were designed from the start to be fault tolerant. In order to register a domain with Network Solutions, you have to prove that you have at least two nameservers, so if one id down, the other will respond.
With Verisign's Managed DNS, they had 4 nameservers for your domain. All appear to be down. The servers are up, you can connect to them and do DNS queries, but they're not returning correct info.
I'm guessing that someone updated the data for all of the nameservers, the data is bad, and now they're frantically trying to find a decent set of backups.
In the meantime, I switched our nameservers to a different company.
>doesn't it take a day to update your whois record to point to new dns servers?
It depends. Your nameservers have a timeout record for your domains which tell other nameservers how long they should cache the info for. If the timeout is high, it will take a long time for your changes to propogate and vice versa.
I made the change about 30 minutes ago and traffic is coming back.