Kixtart logon script 'InGroup' funtion not properly testing domain groups

I have a Win2003 AD with the usual 'Built-In' groups as well as my own 'domain\Security groups'
Next, I've downloaded the latest KixTart (2010 4.6 (but tried several older versions over the course of troubleshooting))

My problem is that the logon.kix script will successfully test the built-in groups and take the appropriate action.  But the statement to test my 'domain\groupname' does not work..

eg:
;This works
If InGroup ("Domain Administrators")
     use R: "\\server\foldershare"
EndIf

;This does not work
If InGroup ("domain\mygroup")
     use R: "\\server\foldershare"
EndIf

;This does not work
If InGroup ("mygroup")
     use R: "\\server\foldershare"
EndIf

I have tried qualifying the group with slashes and domains until I'm blue in the face.
The straight forward Kixtart statements to map drives\folder all work properly (no InGroup test)

Can use InGroup and NOT InGroup properly only if the group is a 'Built-In' group...

Any suggestions on how to get the InGroup test to properly find my own domain security groups?