retrieve serialized java.util.Arraylist in asp.net client (SUID doesn"t match)

I am trying to send persisted objects from a java webservice to the ASP.Net client. Both sides have the object-classes, with the same SerialUID's. Classes without (Array)Lists pose no problem, but when I want to send objects including ArrayLists, the expected SUID is incorrect:

[java.io.InvalidClassException] = {"the class does not match the class of the persisted object for cl = java.util.ArrayList : __SUID = 8683452581122892189, getSUID(cl) = 9195509126275115639"}

Serialization is implemented using binary formatting, not XML because with XML we have circular references between the persisted objects. Using J# at client side, by expecting a java.util.ArrayList instead of an IList or a System.collections.ArrayList doesn't change anything.

Any help would be greatly appreciated!