Your game files do not match the servers. Try verifying your game cache in steam or maybe an update just came out.

[PMystic]

Game is fun but this happens after about 10 minutes of playing. Am interested in a fix otherwise
its not worth playing.

[Fayl]

did u actually try verifying ur game?
if u have, try restarting ur comp at the very least

[JCD2150]

Technical Support that way please http://forums.unknownworlds.com/categories/technical-support