I thought I was out of the woods...

Having gone thru a configuration nightmare for various things on Tomcat, I thought Weblogic might be easier. It wasn't. But I got thru it. Annoyingly, when I came back to the Tomcat webapp, it didn't work again. What's going on??
What I did find was that my app couldn't find any JNDI context at all. It just reported java:/comp/env not found - which I hadn't seen before and couldn't figure out why it was doing it. Then I chanced upon a comment that it is a problem if the naming-*.jar files are in the webapp's own lib. They should just be in Tomcat's common/lib. I thought it sounded pretty unlikely but tried it and it worked!! I restarted and found that I did have access to JNDI items where previously there was nothing. So I thought I'd better note this down, just in case...