errors "Unable to locate Spring NamespaceHandler"

[MiB]

I got these errors in STS 2.6.0M2:

Unable to locate Spring NamespaceHandler for XML schema namespace [http://www.springframework.org/schema/security]

and

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

complaining about errors in my applicationContext-security.xml file in my Roo 1.1.2 generated main project. I never touched this file and it did validate repeatedly.

I made another Roo project from scratch with one entity, MVC and security setup, I compared the applicationContext-security file I had in my main project with the fresh one and they were identical in content. I compared the pom's in case there were a difference in versions of the Spring projects used. There were none.
Finally I copied the fresh applicationContext-security file and replaced my erroneous file in my main project. Problems disappeared.

Problems of this kind can drive a developer crazy. Am I the only one?