I recently built a new computer and have been monitoring the temperatures. They temperatures of the 4 cores during gaming appear to be too hot but I am not an expert on what temperatures I should expect. Also the motherboard temperature seems high. I have not done any overclocking to my system. After gaming for a while I recorded these temperatures using CPUID, Speedfan, and Everest Ultimate at the same time. I am currenty running the 4 fans that come with my Antec 902 and one optional 120 mm side fan. The 4 stock fans are running at their highest settings.
Intel Core i7 930
XFX Radeon HD 5870
Corsair Dominator (3 x 2Gb)
Those are not save temps for a non-overclocked system!!! You have a heat sink application issue. I would highly recommend taking your heat sink off, clean off the thermal compound, re-apply the correct amount of new thermal compound (AS5 or ICDiamond) and make sure the heat sink is fully secured.
Re-test temps after completing the re-application of your heat sink.