Hjælp til exception og aspnet_regsql.exe

Hejsa...til tider opstår nedestående fejl på mit site:

[IndexOutOfRangeException: Index was outside the bounds of the array.]
  System.Data.SqlClient.SqlDataReader.ReadColumn(Int32 i, Boolean setTimeout) +342
  System.Data.SqlClient.SqlDataReader.GetDateTime(Int32 i) +21
  System.Web.Security.SqlMembershipProvider.GetPasswordWithFormat(String username, Boolean updateLastLoginActivityDate, Int32& status, String& password, Int32& passwordFormat, String& passwordSalt, Int32& failedPasswordAttemptCount, Int32& failedPasswordAnswerAttemptCount, Boolean& isApproved, DateTime& lastLoginDate, DateTime& lastActivityDate) +1027
  System.Web.Security.SqlMembershipProvider.CheckPassword(String username, String password, Boolean updateLastLoginActivityDate, Boolean failIfNotApproved, String& salt, Int32& passwordFormat) +106
  System.Web.Security.SqlMembershipProvider.CheckPassword(String username, String password, Boolean updateLastLoginActivityDate, Boolean failIfNotApproved) +43
  System.Web.Security.SqlMembershipProvider.ValidateUser(String username, String password) +81
  System.Web.UI.WebControls.Login.OnAuthenticate(AuthenticateEventArgs e) +131
  System.Web.UI.WebControls.Login.AttemptLogin() +106
  System.Web.UI.WebControls.Login.OnBubbleEvent(Object source, EventArgs e) +82
  System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +35
  System.Web.UI.WebControls.Button.OnCommand(CommandEventArgs e) +86
  System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +155
  System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +7
  System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +11
  System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +33
  System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4921

Jeg har googlet fejlen og fundet:
http://forums.asp.net/p/936678/2068007.aspx
http://msdn.microsoft.com/da-dk/library/x28wfk74(en-us,vs.80).aspx

Vil lige høre jer, er det noget i har erfaring med, at bruge det lille program? og kan fejlen skyldes noget andet? Tilsidst, ændre programmet KUN aspnet stored procedures UDEN at påvirke eksisterende data i databasen?

Mvh. PabloPablo