java.lang.ClassNotFoundException: org.springframework.web.context.ContextLoaderListener

I had a similar problem when running a spring web application in an Eclipse managed tomcat. I solved this problem by adding maven dependencies in the project's web deployment assembly.

1. Open the project's properties (e.g., right-click on the project's name in the project explorer and select "Properties").
2. Select "Deployment Assembly".
3. Click the "Add..." button on the right margin.
4. Select "Java Build Path Entries" from the menu of Directive Type and click "Next".
5. Select "Maven Dependencies" from the Java Build Path Entries menu and click "Finish".

You should see "Maven Dependencies" added to the Web Deployment Assembly definition.

Same thing happens to me from time to time when using Eclipse WDT. Its specialy frustrating when this happens to a unmodified and previously working project. This is what I do to fix it in this last scenario:

1. Stop Tomcat (if it's running)
2. Open the "Servers" view: Window > Show view > Other > Server > Servers
3. Right Click on Tomcat Server > Clean Tomcat Work Directory.
4. Right Click on Tomcat Server > Clean
5. Restart the server

This usually fixes the issue you mention.

You could try "Clean Tomcat Work Directory" or simply "Clean..". This supposed to discard all published state and republish from scratch.