For a very long time I have been unable to have hot-deploy work under Tomcat, as Tomcat would lock some random JARs. This meant to redeploy I had to shutdown Tomcat, delete the JARs, start Tomcat and deploy the application. It was slowly driving me insane.

Luckily I found the answer here - I Put A Spell On You, Because you're mine: Aka Why is TomCat Holding Onto Jars?. Glad I was not alone in having this problem.