My most common headache during my last Spring project was:
during start of Tomcat.
Every source pointed to problems with spring.jar, so I suspected having some version conflict between my Spring libraries (eg. I used also Spring-WS in an old version). But that wasn’t real cause and I’d wasted a lot of time. The real problem was faulty Eclipse IAM plugin.
Try out some tricks I’ve described in my another article : Problems using Eclipse IAM and Maven
They really may help you.