VGA cables not all the same!!

VGA cable pinouts can vary.

"Classic" VGA:
1 Red (Analog) 
2 Green (Analog) 
3 Blue (Analog) 
4 Reserved 
5 Ground
6 Red Return 
7 Green Return
8 Blue Retuen
9 No Connect
10 Ground
11 (ID0) GND (Color)
12 (ID1) NC (Color)
13 Horzontal Sync
14 Vertical Sync 
15 No Connect 

newer standard 

"VESA DDC2"
Pin 1 RED Red video
Pin 2 GREEN Green video
Pin 3 BLUE Blue video
Pin 4 N/C Not connected
Pin 5 GND Ground (HSync)
Pin 6 RED_RTN Red return
Pin 7 GREEN_RTN Green return
Pin 8 BLUE_RTN Blue return
Pin 9 +5 V +5 V DC
Pin 10 GND Ground (VSync, DDC)
Pin 11 N/C Not connected
Pin 12 SDA I?C data
Pin 13 HSync Horizontal sync
Pin 14 VSync Vertical sync
Pin 15 SCL I?C clock

source 

arximastoras.blogspot.com