RT Hangs when changing access control settings

When Modifying user permissions (Admin/Users/Modify.html?id=xx) I uncheck
the box for “Let this user be granted rights” and submit changes RT Hangs. A
strace against the apache process reveals the system is stuck in an infinite
loop executing the following query:

SELECT * FROM CachedGroupMembers WHERE Disabled = ‘0’ AND GroupId = ‘4’ AND
MemberId = ‘1’

This problem does not occur on fresh installations of RT. I can only
reproduce this error after importing my existing RT Database into the fresh


RT 3.4.1 (Also seen on 3.0.12)

MySQL 4.1.11