Faulting application w3wp.exe

I have created an web application and an WCF service in VS 2008 on IIS 5.1 Windows XP SP2 environment.
Default web site settings are application protection is medium (pooled) and identity is IWAM_.
Now I have deployed both on IIS 6.0 Windows Server 2K3 SP2 environment.
web application and WCF service are hosted in defaultapppool.
Problem - I am able to browse the ASPX page but when I submitted it which uses WCF service, it shows an error in application log and page stop responding.
Faulting application w3wp.exe, version 6.0.3790.1830, faulting module
unknown, version 0.0.0.0, fault address 0x01275c90.