Maybe there was too much traffic on the block, I'm not sure. I think it just meant the node was overloaded and blipped out. I see that every once in a while, usually I just wait 3 seconds and it resolves. Hopefully HIVE devs can resolve this issue and get to the bottom of it. Thanks, maybe we should ask @themarkymark????
If you continue to have problems maybe try to switch nodes in your hive keychain preferences, I use ANYX right now because it's more reliable!