: The reason why this assert hits you in one of your tomcat installations : could also be related to some instrumentation tools you have enabled in this : tomcat. Lot's of instrumentation tools may dynamically change class bytecode : and e.g. make them unfinal. In that case the assertion of course fails (with : assertions enabled). Before saying Solr 3.1 is not compatible with Java 1.5:
It's also possible that whatever packaging of Java you are using; and the way your are running tomcat; is subtlely differnet between your Java5 and Java6 installs such that Java5 is run with assertions by default but Java6 is not. -Hoss
