Ok, so here's my problem: A plugin needs to load classes. These are not in the plugin's own dependencies, because they're specified by users in the plugin configuration. Please see the attached sample that demonstrates this fails. The test.sh file first installs the dummy plugin then runs it. (I left a dependency on commons-collections in the plugin's pom, just because at first I thought it failed when class instanciated by the plugin depended on classes of the plugin's self dependencies, but it doesn't seem to be the case) For the record, I bumped into this when trying to make a maven2 plugin for xdoclet2 - which uses picocontainer to instanciate its own plugins. Cheers, g