Error message - abuse of IP address

I am a teacher and we are using your validator to check our documents. When the student finds an error and then fixes it and rechecks, we get an error message:
[cid:image001.jpg@01D202BF.D9DF39E0]
Our IT guy says this problem is on your end and because we have one IP address going out and it appears as if they are from the same machine when they aren't. Any help or suggestions?





NOTE: Whenever possible, give the address of the document you were checking..