I'v run into this problem before, and I hit it again tonight:
http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/80ed858a-64e3-4821-a1a3-44940fbf4e83

How about this for a solution - In my DataAccess class, whenver I receive a DbParameters collection, simply make a local copy of
each parameter, place each copy into a new collection, then assign that collection to the DbCommand object?

This way, my collection of parameter never really gets used, like this:

private List<DbParameter> _CopyParameters(List<DbParameter> Parameters)
{
    List<DbParameter> RetVal = new List<DbParameter>();

    foreach (DbParameter Param in Parameters)
    {
        DbParameter NewParam = _Factory.CreateParameter();
        NewParam.ParameterName = Param.ParameterName;
        NewParam.Value = Param.Value;
        NewParam.Direction = Param.Direction;

        RetVal.Add(NewParam);

       Parameters.Remove(Param);

    }

    return RetVal;
}

Then use it like this:

public int ExecuteNonQuery(string Command, List<DbParameter> Parameters, CommandType CommandType)
{
    int RetVal = 0;

    DbCommand cmd = _GetCommand(Command);

    try
    {
        RetVal = cmd.ExecuteNonQuery();
    }
    catch (Exception e)
    {
        throw;
    }

    return RetVal;
}

Then in _GetCommand()...

private DbCommand _GetCommand(string Command, List<DbParameter> Parameters, CommandType CmdType)
{
    _GetFactory();
    _GetConnection();

    DbCommand cmd = _Factory.CreateCommand();
    cmd.CommandText = Command;
    cmd.Connection = _Connection;
    cmd.CommandType = CmdType;

    if (Parameters != null)
    {
        List<DbParameter> NewParams = _CopyParameters(Parameters);

        cmd.Parameters.Clear();
        cmd.CommandType = CmdType;

        foreach (DbParameter p in NewParams)
        {
            cmd.Parameters.Add(p);
        }
    }

    return cmd;
}

I implemented this and it seems to work. Thoughts?