desync. (some extra words to make the length of the title longer because only "desync" as title is too short)

I really enjoy playing vamp ultra.. but since a few weeks i have desync all the time.. i really dont know why or how because before i had all those desyncs vamp ultra worked fine, and i never had a desync before. anyone knows why i have desync and how i can fix this?

You can't, Many people refer to them as "server splits" on B.Net, because they think that the server kicked them off, or they had a connection issue with it. In essence, your game "splits off" from the others. You're following an alternate timeline. You're still playing the game, but nobody else is there. Nobody is chatting back, their units are only still moving if they were following previously-issues orders... Everyone just dropped out. That's desync.
How? When there's an error; an inconsistency. Sometimes it's just an error with the map. A mapmaker might have made some particularly bad coding, or they just used so much leaky GUI (enough to make initialD's head completely pop off!) that WC3 couldn't take it. Or, it can be something else. Third-party programs (maphacks, etc.) can contribute to the problem. If you try adding cheats like -gold into a collided map... It instantly causes a desync. Everyone is playing the same game, and all of a sudden, your game thinks you have a different amount of gold than everyone else's game thinks you do. And there's a desync.