[ExchangeList] Modifying Distribution List

I have a mixed mode Exchange Server environment both exchange 5.5 and 2003

We have ADC running fine and all replication are working fine between Active directory and exchange 5.5

I have a distribution List in Exchange 5.5 and user is given second owner permission for the DL and the user mailbox is in Exchange 2003

Now the user after given permission is not able to modify the DL cannot able to add and delete memebers

I did not fine any problem in replication of ADC

But even now user is not able to modify DL and user is getting you do not have sufficient permission

What could be the problem can anyone assit

Regards

Sabeer