Problem whit Accept in Socket connection

Dear Forum

My little server is using a socket listner.As normally, i do the .Start() and the .Accept..() .After the accept i create a new thread witch take in input the new stream created by client connection..and all work ok.The Accept is inside a while (true) loop, so i can menage as much client i want.

The problem is when thread's created, make the polling on a buffer witch tipe come from a .DLL (menaged DLL). Es List<tipe classA> where classA comes from DLL.

If i use a tipe not from .DLL, the no problem.
(DLL i need because i need to serialize a object)

Thanks
Roberto