Access Violation

Yazdigimiz programda bazen assagidaki hatayi aliyoruz, bu hatayi nasil duzeltebilirim?

Hata:System.Web.Services.Protocols.SoapException: Server was unable to process request.
 ---> System.Exception: Access violation at address 00000000.
Read of address 00000000 DLLName=D:\Netsis\FUSION06\Ortak\EphesDLL.DLL
 DLLName=D:\Netsis\FUSION06\Ortak\EPosta.DLL DLLName=D:\Netsis\FUSION06\TemelSet\DIZAYN.DLL --->
System.Exception: Access violation at address 00000000.
Read of address 00000000 DLLName=D:\Netsis\FUSION06\Ortak\EphesDLL.DLL
DLLName=D:\Netsis\FUSION06\Ortak\EPosta.DLL
DLLName=D:\Netsis\FUSION06\TemelSet\DIZAYN.DLL --->
 System.Runtime.InteropServices.COMException (0x8000FFFF): Access violation at address 00000000.
Read of address 00000000 DLLName=D:\Netsis\FUSION06\Ortak\EphesDLL.DLL
 DLLName=D:\Netsis\FUSION06\Ortak\EPosta.DLL
 DLLName=D:\Netsis\FUSION06\TemelSet\DIZAYN.DLL at NetOpenX40.FaturaClass.kayitYeni()
at Bilser.Web.Services.NetsisClient.NClient.SaveFatura(User _user, FtUst _ftUst, Boolean insert, String _root, String _username, String _password) ---
 End of inner exception stack trace --- at Bilser.Web.Services.NetsisClient.NClient.SaveFatura(User _user, FtUst _ftUst, Boolean insert, String _root, String _username, String _password) ---
 End of inner exception stack trace --- at Bilser.Web.Services.NetsisClient.NClient.SaveFatura(User _user, FtUst _ftUst, Boolean insert, String _root, String _username, String _password) ---
End of inner exception stack trace ---

hiç biri degil maalesef,program zaten çalisiyor,ama yogun kullanilirsa bu hatayi aliyoruz,iis reset atlinca düzeliyor daha sonra tekrar basliyor hata vermeye.