First thing you could do is try to start up a game, not with Default Add-Ons, with no Add-Ons enabled.
Play for the average-ish for the game to crash, if it does not crash restart with Default Add-Ons enabled.
If the game will crash later one, your Default Add-Ons are corrupted, best you could do is reinstall or ask someone for their Default Add-Ons.
If the Default Add-Ons on do not crash the server after awhile, it's one of your downloaded Add-Ons.
If game wiht no Add-Ons enabled crash the server, you are forgeted, the problem is either integral either from your hardware and best you could try is reinstalling Blockland, if the problem still persists make a Help topic instead in the Help category.