Not checking to see if your Cas Latency is turned to 2 instead of 3 is a big mistake made by most newbie overclockers. Most motherboards default to cas3 which is not what you probably want. Most problems that arise from dust and impurities leads back to problems with heat. What we mean by impurities is oils and grease and dirt that come into contact of the bottom of your HSF and the top of whatever you are trying to cool with it. If you have dirt and oil from your hands, your thermal grease will not work as well, and if you are using thermal tape or thermal epoxy, the bonding quality is lowered immensely.
Dust is a problem for a few of reasons.
If you have dust that has settled on your motherboard and other components, it will not let heat escape. Dust will settle into heat sinks, blocking air flow through them, thus your fan that is blowing over your heat sink is not achieving much. Lastly dust is the number one killer of fans. It slows them down causing more heat from friction and reduces air flow and will eventually make them stop rotating altogether. PCI Cards that are Unwilling to Run at Non-Standard Bus speeds.