DHCP Problems

I have 2 x Layer 3 GSM7328FS which have around 10 VLANs running off them, however we are having a major issues with our computers not installing domain push via group policy. When we have investigated this issue there is allways a log in the entry of all the computers saying the following "The name "IT :1d" could not be registered on the interface with IP address 172.16.x.x. The computer with the IP address 172.16.x.x did not allow the name to be claimed by this computer." now all of our computer have a independent asset number and non of them have are name the same as they are named off there asset number. How as you can see from the above the name seems to be dropped in place of "IT :1d". Now i have narrowed this down to the router which is dropping the data as for example the names of my machines are IT1234. Is ther anything i can do to fix this, the clients use the IP Helper address which is a UDP system. If you need a complete dumb of the config, i am willing to give you this.

Regards,

Stuart