Rules Violations Exceptions in LINQ ASP.NET MVC

Question

Possible Duplicate:
First attempt at Linq to Sql in NerdDinner - Rule violations prevent saving

Hello,

I am using ASP.NET MVC application with LINQ and when I try to SubmitChanges after Inserting a table data I am Getting "Rule violations prevent saving".

I am doing UpdateModel before submitting but that passes fine. I double checked my FKs and everything is alright

What else could be the problem?

My Code

db.Contacts.InsertOnSubmit(ContactInfo)
 db.SubmitChanges()

Thanks in advance.