Changing case for client principal in windows XP

[DM]

I have test on both SP1 and SP2 windows XP.

Using Kerbtray I can see my client principal seemingly randomly become 
upper and lower case throughout the day.

We are use a GSSAPI/Kerberos enabled putty for no password single 
sign-on to HP-UX and linux.  When the client principal becomes capital 
this obviously does not work.

Does anyone know how to make Windows XP use only lower case principal 
names?  It seems everything but XP follows the user at REALM convention.

Any help is appreciated.

Thanks,
DM