When I try to run Ethereal, why does it complain about sprint_realloc_objid being undefined?
Ethereal can only be linked with version 4.2.2 or later of UCD SNMP. Your version of Ethereal was dynamically linked with such a version of UCD SNMP; however, you have an older version of UCD SNMP installed, which means that when Ethereal is run, it tries to link to the older version, and fails. You will have to replace that version of UCD SNMP with version 4.2.2 or a later version.