My keyboard randomly stops working

[coldraven]

The keyboard on this laptop keeps failing, most usually within an hour of being switched on.
If I reboot it works again, logging out does not work because I cannot enter a password.
This problem seems to have started after I removed the keyboard to clean the fan although I did not disconnect the ribbon cable. I did have a look to see if I had trapped or damaged the cable but could not see anything obviously wrong.
Anyone have an idea of what is going wrong?

The laptop is an HP Compaq 6715b

[coldraven]

Solved!
I finally got up the courage to disconnect the keyboard completely.
I was worried that I would break the flimsy ribbon cable, I was unsure of how the connector released. It hinged upwards!
I gently cleaned the ribbon connectors with a dry cotton bud.
The keyboard has three cylindrical metal supports into which the retaining screws locate. Two of these make contact with pads on the mother board but these pads were discoloured black.
I gave then a gentle scrape with a screwdriver to reveal the copper underneath.
Whether the keyboard needs to be earthed in this way I don't know but it's working fine now.
I was getting really annoyed at having to reboot every hour or so.