NT Roaming Profiles

We have a NT4 network with approx 400 users and all use roaming profiles. We have limited the profile storage space to 10MEG for each user. What we do get is an error message saying that users have exceeded their storage space but when we check their profile it is less then 10MEG but a file called USER.DMP is causing the error and this is over 10MEG. Does anyone know what this (USER.DMP) is and why it exceeds the profile space?