I had this problem in Tomcat 7 and the reason was that I had antiResourceLocking set to true (it sounded like a good idea...).
According to the docs ( http://tomcat.apache.org/tomcat-7.0-doc/config/context.html ):
Please note that setting this to true has some side effects, including
the disabling of JSP reloading in a running server: see Bugzilla
In my case it even caused plain static text files to be cached.
So, in summary, at least for rapid development I had to use: