I have the same problem. "No Input Signal"

I am using an HP L1706 monitor... This issue happens at random times but I was able to fix them just by turning off my computer and for some reason when I check the back of the tower... reconnect and disconnect the VGA cable it'll work. But last night the problem happened again. I tried to do the same thing and it is still not working. Thinking that it's not the monitor or the VGA cable that's causing the problem I tried to connect my SAMSUNG SyncMaster 753 DFX monitor using also a different VGA cable. Still the same problem happened.

It might be the tower itself that's causing the problem. I've noticed that the motherboard's green LED is not lit. Though theres is power because all the fans are working. Even the GeForce 9500 GT fan is working.

Can it be the motherboard??? I'm using a FOXCONN G31MV Series motherboard, 4GB RAM, Core 2 Duo processor, 250GB SATA HDD, and a GEFORCE 9500GT video card.