When invoking getBean(...) from within a PrivilegedAction and the bean is not yet initialized (scope="prototype") it gets created inside PrivilegedAction in the AbstractAutowireCapableBeanFactory. But without propagating the outer(calling) AccessControlContext. So if your bean creation(initialization) relays on the calling context, it will fail.
The issue was introduced after the fix of http://jira.springframework.org/browse/SPR-4017
I can also provide a simple test case, if it's needed.