Do you have another monitor or a friends monitor you could try as a diagnostic tool for a few mins.
Sounds like you all ready know whats wrong just need the proof..So I think its the VGA port on the monitor because it happened my old computer too.
My Computer
- Computer Manufacturer/Model Number
- Custom
- OS
- Windows 7 Ultimate 64bit
- CPU
- Intel i5 650
- Motherboard
- Intel DQ57TM
- Memory
- G.SKILL 8GB DDR3 1333
- Graphics Card(s)
- Radeon HD 5770
- Sound Card
- Realtek
- Monitor(s) Displays
- 2 - LG W2061TQ
- Hard Drives
- OCZ Vertex 2 60GB
Seagate Barracuda 320GB
- PSU
- Antec EarthWatts 650W