I've got a MacBook Pro with a 19" LCD (HPL1906) connected with the dvi-to-vga connector. The Mac is my secondary machine, so I don't have an external keyboard/mouse connected directly to the Mac; I'm using synergy through my primary Windows machine. I've got the Mac set up to wake on lan, so when it's sleeping, I can wake it up from my Windows machine. Synergy will then connect to it within a few seconds, but the external monitor can take up to ten minutes to turn on. During that time, the light on the monitor is flashing, but nothing shows on the screen. When it eventually does come up, it auto adjusts, and then it's fine. I've tried plugging in external devices (like a mouse) during this time, and unplugging/replugging the monitor cable, and sometimes that will work, but not every time. Any ideas why it takes so long to turn on?
Edit: Sometimes if I plug something in to the USB ports - like an external mouse, or an iPad - the monitor will come up within 30 seconds or so, but not every time.