Ok I have a very weird situation. I have a monitor (HP 2311x) that doesn't work with my macbook air (core i5, 11" 2gb ram). It works with an hp laptop, a macbook pro, and another macbook air (same model as mine). Now you might think my MBA's thunderbolt port is faulty, but I'll tell you this: It does work when connected to my TV! It just doesn't work with the monitor! I really don't understand it, because a same model MBA does work with the monitor too... All connections described above are MDP->HDMI. Also, I reset the SMC and pram-vram and still doesn't work. Should I try a format and clean install of Lion? I also tried connecting to the monitor in boot camp with windows 7, still no luck! edit: I did click on "detect displays". Any useful tips and knowledge appreciated (read my post before suggesting what I've already done, though).