local/NIS group issue

I have a strange issue with one CVS repository on cvshost,
and maybe you can help...

when a person who is a member of the arcx123 NIS group attempts a checkout
from /---/---/arcx123/---/---/---which also belongs to the arcx123
group, the server returns an error that a lock file could not be created
in that directory due to insufficient permissions.

When the arcx123 group is also defined in the local /etc/group file on
brooks, that problem disappears.

Setting the sticky bit for group or user on the files in the
repository continues to produce the same error if the group is not
defined locally.

/etc/nsswitch.conf is just like any other server's. groups are looked up
first in files then in NIS. This problem happens only on this repository
also.