Well... after testing DepFinder presented above, it turns out it is great for a quick detection of simple dependencies, but it does not scale well with the number of classes...
So the REAL ACTUAL ANSWER is:
CDA - Class Dependency Analyzer
It is fast, up-to-date, easy to use and provides with graphical representation of classes and their circular dependencies. A dream come true ;)
You have to create a workset in which you enter only the directory of your classes (.class) (no need to have a complete classpath)
The option "Detect circular dependencies - ALT-C" works as advertise and does not take 100% of the CPU for hours to analyze my 468 classes.
Note: to refresh a workspace, you need to open it again(!), in order to trigger a new scan of your classes.
