LINQ Return Single Type Of Object Invalid Cast

Ok, just needing a 2nd set of eyes looking at this to make sure the error isn't something else other than my LINQ code here. Here's the function class itself:

Public Function GetJacketByPolicyID(ByVal jacketID As Int32) As tblPolicy
Dim db As New DEVDataContext()
Dim j As tblPolicy = db.tblPolicies.Single(Function(p) p.policyNumber = jacketID)
Return j
End Function

and here is the code which calls this class function in the web control form itself:

Dim p As tblPolicy
Dim j As New Jackets()
p = j.GetJacketByPolicyID(3000050)

For some reason it's flagging the 2nd line in the GetJacketByPolicyID function saying the specified cast is not valid. So I'm guessing it's something I'm doing wrong. I'm sure the tblPolicy/tblPolicies class works right since I can create a new instance of a tblPolicy and set a few variables by hand and return it, so that's not it. I've also checked the datarow I'm fetching and there's no null values in the record, so that shouldn't be it either.