This is an old thread, however it's one of the main results for Google. So here's the final answer on how to resolve this. As you can see, it mentions "[buildcraft]" in the nocheat, it means this "user" as it is identifying it is trying to place blocks out of Minecrafts default reach. To fix this, add the nocheat bypass permissions node to the user "[buildcraft]" (without quotes.)
or
Simply op the user "[buildcraft]"
Problem Solved.