|cleaning the edge connectors; how should I do that?|
You take out the RAM sticks, then run a clean pencil eraser over the edge connector contacts. I usually then pop them in and out a few times to ensure there is not oxide on the edge connectors themselves.
If you have a separate graphics card do the same for that and any other edge connectors.
This is not guaranteed to help but it is easy to do and can often cause strange symptoms.
Always pop back and let us know the outcome - thanks