So when I use bukkit, here'S what I get

Wrong location! net.minecraft.server.EntitySheep@11c5
-182.402241727446,104.34753624753483(-12,6) vs -11,6
Wrong location! net.minecraft.server.EntitySheep@11c7
-152.73110674975672,237.44999998807907(-10,14) vs -11,14
Wrong location! net.minecraft.server.EntitySheep@11c8
-158.18072697969282,235.44999998807907(-10,14) vs -11,14
Wrong location! net.minecraft.server.EntitySheep@11cb
-187.85462711084128,278.8859953852643(-12,17) vs -11,16
Wrong location! net.minecraft.server.EntitySheep@11ce
-165.48352871321075,321.48350473531883(-11,20) vs -11,18
Wrong location! net.minecraft.server.EntitySheep@11cf
-150.57757142631905,321.5347798150943(-10,20) vs -11,18
Wrong location! net.minecraft.server.EntitySheep@11d0
-176.1145295997433,325.61783986897046(-12,20) vs -11,18
xXModz lost connection: disconnect.quitting

And when I start the server again, everything is reseted

help