Common mode choke polarity

[ed181]

I've been having a problem where my circuit fails the negative burst test (-2000 V, L+N) on the power supply when the I have a common mode choke connected the correct way round and when I change it round it fails the positive burst test (+2000V, L+N) but passes the negative. Has anyone ever had any similar problems?

 

[Arouse1973]

How is it failing, what standard, directive are you working to? Is this just the standard conducted immunity testing? This is strange as a common mode choke is normally good at this sort of thing.
Can you post circuit diagram and what choke you are using
Adam