Machine's ip seem to change randomly

Hi,

We have around 300 group. The groups contain machines from diffrent remote branches. one particular client machine in a group seem to change ip address frequently. initially, i thought the machine was wrongly put in a diffrent group but when the machine was moved to correct group, it again changed the ip which belonged to a different group(ip range). The common thing which was found was that all this machine have a common computer name. Is this any bug ? Please help..

Regards,

Anish