From the command line, CLASSPATH is empty,Maybe that's the problem?
so somewhere in Ant, Tomcat and/or JRE configs are settings that resolve where stuff is installed.Maybe the problem is that there aren't? (As in, if the CLASSPATH env-var is empty, *no wonder* the IDE thinks "the classpath is incomplete"...(?))
But I can't figure out how to get Eclipse to find what it needs.Have you tried setting the CLASSPATH environment variable before starting the IDE?
Not that I have the fucking faintest; just guessing... HTH, anyway.