soap server application fauleted error...pls sugg

hi..


i have created a fucntion to attach note ! i can update that particular

contact details, so it means the contact exists. but some how i am
getting error "SOAP SERVER APPLICATION FAILED"


here is what i am doing
Dim mobjBizUser As New BizUser
Dim mobjNotesManager As New CRMNotesManager
dim strNotesId as string
Dim mobjNetworkCred As New
System.Net.NetworkCredential(gconUserName, gconPwd, gconDomain)


mobjBizUser.Credentials = mobjNetworkCred
mobjBizUser.Url = mstrDir & "BizUser.srf"


mobjNotesManager.Credentials = mobjNetworkCred
mobjNotesManager.Url = mstrDir & "CRMNotesManager.srf"


Dim mstrErrorMsg As String
Dim mstrUserName As String
Dim mstrUserId As String


Try
Dim mobjUserAuth As CUserAuth = mobjBizUser.WhoAmI()
'mstrUserName = "ADVWORKS\tester1"


Dim mUserXml As New
System.Text.StringBuilder("<annotation>")
mUserXml.Append("<subject>Sample note</subject>")
mUserXml.Append("<isdocument>1</isdocument>")
mUserXml.Append("<ownerid>" + strContactID + "</ownerid>")
mUserXml.Append("</annotation>")


strNotesId = mobjNotesManager.Create(mobjUserAuth,
mUserXml.ToString())


Catch ex As Exception
Return ex.Message


Finally
mobjBizUser = Nothing
mobjNetworkCred = Nothing


End Try
Return True