Interfaces and Classes between Projects
Naming  

IDBUtils is a name for a namespace, but for an interface representing a database system it is poorly named. Better use something like IDatabase, IDatabaseServer or IDatabaseSystem.  

OpenConnection()

This method can be simplified by removing the success variable and also using a guard clause, which reduces horizontal spacing.  

public static bool OpenConnection()
{
    if (String.IsNullOrWhiteSpace(DBConnectionString.Length))
    {
        return false;
    }

    try
    {
        conn = new SqlConnection(DBConnectionString);
        conn.Open();
        return true;
    }
    catch { /* Do nothing... */ }
    return false;
}