Hmm seems to me maybe the video card in your PC isn'[t switching on. have you got the monitorplugged into the right port? You might have two inside your pc (one in an agp slot (or pci-e slot) and one on the motherboard, so try finding another VGA connection.
The bios reset could have worked before maybe because it might have switched on/off the onboard video making it power up the monitor, so thats why you should check the connection.
I hope this heps