Is the JSP page you've changed included inside another JSP page? If so, you would have to make a change to the parent page to see updates. Very annoying in my opinion!!
Otherwise, another method I've seen solve this problem is by going into the 'work' directory, finding your appropriate web app folder and there you will find your compiled jsp classes. Delete those stubborn classes to force the container to recompile them.
One possible cause for this is that the system time on your server is out of sync with the one on your workstation.
Tomcat looks at the last modified date of the JSP files to determine whether or not it has been updated since the last recompile. If you're moving files to the server with dates older than the last recompile, Tomcat will never know to re-generate the servlet code.
If the server is a Unix box the touch command can be used to update the date of the file(s).