Just purchased my first cabriolet...an 05 320 cab fully loaded (obsidian black, command, sirius, cd changer, xenon) and every time I go over any significant bump, (ex train tracks at 2 mph) I get the "close top" warning. I just wanted to see if anyone has experienced this and if there were any more "surprises". As a side note, what the best method for maintaining the top?