Twin UID's

Just today our DBA support group came across this little feller:  One of our Oracle 11R2 instances running on Linux using LDAP suddenly started to no longer allow users who were logging in via putty to execute CTAS's or SQL*Loader.  Oddly however, they could execute SQL*Plus with no issues.  After troubleshooting the issue it was found that a LDAP group was created with the same UID as Oracle's.  Once the new group received a unique UID the problem went away.