it means there's a lot of lag. Either the server is hosting more people than it should for that connection, or you're on a weak internet connection (like a 56k, no offense to 56kers, I used to be one). There is very little you can do. If you're a 56k, try typing this in console. Rate 4000 (4000 seems like a good value I think). Or try various values between 1 and 9999, 1 being the low end and 9999 being the high end (for broadband users). Try and find what works best for you. In the end, therte's not always a lot you can do about latency.
As for the actual definition of the error, I think the game literally flushes all game entities and reloads them.
-Karrde-