Do you have any <import> tags in any of those configuration files? And maybe those <import> config files, have <import> tags. But somewhere you are looking up that config file.
Or do you have any Java COnfiguration classes with @Configuration that are @ImportResource other config files?
Oh yes, I figured out what the problem was. My JUnit test class extends from another super class and in that super class, there was a reference to the aop-config.xml. I do not know who has added it. Guess it could be due to eclipse auto fill feature or something else. I removed it and it all started working again.