Multiple User Profiles Created at EACH logon

Everytime a select group (approx 50%) of my users log onto my Windows Server
2003 terminal server box they get two profiles.
For instance, user chindle will have two profiles created. One will be
'chindle' and then he will have another one called 'chindle.machinename'.
Does anyone have any idea why?
I am also using Citrix Metaframe PS 4.0.
I was previously using roaming profiles but encountered the same issue. I
have since switched back to local profiles and enforced this in GP.

Any ideas would be much appreciated.