Beans imported by bean-import - problem with AOP proxies?

General question: What are the differences (if any) between beans imported to the flow by <bean-import> and beans defined in "standard" way (for example beans defined for root application context in some XML config file)?

I've encountered a problem while integrating Spring Security in my app (using Spring Framework 3.1.1.RELEASE, Spring WebFlow 2.3.1.RELEASE and Spring Security 3.1.0.RELEASE).
I've noticed that Spring Security annotations are not working in beans imported by <bean-import> and are working just fine in beans defined in a "standard" way.
I've also defined several aspects in my app and it's the same issue with them (working in "standard" beans and not in beans imported by bean-import).

I probably have some sort of a problem with AOP proxies that, as I believe, are supposed to be generated for beans covered by my aspects' pointcuts and beans with methods annotated with SS annotations.

Same issue with SS annotations is present with my aspects "switched-off" (i suspected there might be some sort of a problem with generating a proxy for a proxy, but that's not it).
I've also tried both, with and without the proxy-target-class attribute set to "true" in global-method-security tag.