System.Runtime.InteropServices.COMException Message:

System.Runtime.InteropServices.COMException Message:

I have converted my 32 bit web Application into 64 bit and deployed it on
a 64 bit machine all the modules are working fine but one. Why does this
one throw this Exception?
System.Runtime.InteropServices.COMException Message: Retrieving the COM
class factory for component with CLSID
{494A8C73-FA00-43A7-9F1D-6DBF80EC2B63} failed due to the following error:
80040154 Class not registered (Exception from HRESULT: 0x80040154
(REGDB_E_CLASSNOTREG)).
What I understand is my code is calling a dll which is 32 bit, but when I
checked in my 64x debug I found it there too.