Monitor problems

The led light on my monitor often flashes green and orange and although the computer sounds like it is booting I cannot see anything on the screen when the led is flashing green and orange. However if I hold the on/off button until it goes off and leave it a minute or two and turn it back on again most times the led is green and stops flashing and the computer boots properly. Also if the lights is flashing green and orange and if I hold the button to turn it off and get it to come on again properly and the computer has already previously booted I get the desktop picture but no icons appear. I then have to turn it off and get the orange and green light to stop flashing and reboot and it is Ok again This is an intermittent fault. Is it a sign that the monitor needs renewing as it is now around six years old - My computer has recently been upgraded from vista to Windows 7 but I don't think this has anything to do with the way the monitor is behaving. I am wondering if I would be best to just buy a new monitor - any thoughts would be appreciated.
Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows 7 Professional, Service Pack 1, 32 bit
Processor: Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, x64 Family 6 Model 15 Stepping 11
Processor Count: 4
RAM: 3326 Mb
Graphics Card: NVIDIA GeForce 8500 GT (Microsoft Corporation - WDDM v1.1), 256 Mb
Hard Drives: C: Total - 475531 MB, Free - 170214 MB;
Motherboard: ASUSTeK Computer INC., P5N-E SLI
Antivirus: avast! Antivirus, Updated and Enabled