Hi Shaji,
This reminds me of an issue when i was trying to access an excel sheet from a .net framework. I had to update DCOM settings for my inet user.
What I did was< Administrative Services--> Component services-->My Comp-->DCOM-->Desired Application type(MS Excel app for my case)--> Properties-->Security-->Activation and Launch Permissions--> Customize --> Edit --> Add User
Try to look into this dimension as well, not sure but I hope it helps.
Thanks,
Swaroop