If you encounter a javax.naming.SizeLimitExceededException when you use the , you might have encountered a maximum size limit. You can modify this limit in the portlet.xml as follows:
<portlet>
<portlet-name>PortalUserGroupSelection</portlet-name>
<portlet-class>
com.novell.afw.portal.portlet.core.permission.PortalUserGroupSelection
</portlet-class>
<init-param>
<name>MIN_CACHE_SIZE</name>
<value>20</value>
</init-param>
<init-param>
<name>MAX_CACHE_SIZE</name>
<value>200</value>
</init-param>
<init-param>
<name>PAC_MAX_RESULTS</name>
<value>2000</value>
</init-param>
Redeploy the User Application after you make this change.