Hope someone can please advise, going nuts here trying to resolve external monitor issue.... Have white MacBook (bought Jan 2007), been working fine with an old external 21" CRT monitor that I used with MacBook lid closed. Running MacBook with Lion 10.7.4 and have a BookEndz dock. In mid-May, decided to replace CRT with LCD monitor. Bought a new ASUS 23" VH238H monitor. Connected it up to my BookEndz dock and it worked fine until the other day. Before, I was able to open up lid, click on power button and then close lid and my external monitor would light up and then would see Mac boot up normally. Now, when I try to use the external monitor I just get the message on display 'HDMI No Signal' and then screen goes black..... Only other weirdness I had recently, is the System Prefs window not opening issue, but fixed that by trashing a pref file and rebooting Mac.... Any suggestions as to how to get external monitor recognized again by MacBook?? Thanks for any and all help.