Most of the 1066 and higher FSB systems run pretty hot Northbridges - obviously the speed of the memory and how much you overclock it also increases the thermal effect.
1. Good case cooling - front and rear fans will help pull air over the heatsink on the bridge and lower the temps..
2. The type of heatsink (passive vs active fan) will effect it. There are some superior quality coolers out there you could upgrade if you were interested ... even watercooling blocks.
3. Some heatsinks are poorly factory fitted with thermal paste - Iv'e found a few with none fitted. It is worthwhile reseating one which is getting very hot. A luttle tip here ... the guts of a biro can help remove those plastic split pin bridge retainers ... push it over the pins forcing them together from the bottom of the mobo.
4. Obstruction to the airflow over the heatsink for the bridge ... some are fitted in a bad spot depending on the layout of the rest of the case and what types of cards you put in it ... so check and loom up the wiring to maximise the airflow in the area for a start.
I'd have concerns if my Northbridge was pushing in excess of 50 C and I couldn't get it down, though Iv'e worked on a couple of boards with higher temps and they still ran like clockwork.
Addressing the majority of thermal issues from the main culprits - cpu, gpu, chipset (Northbridge) and HDD will likely mean a more stable and longer lasting PC.
Since I cane the guts out of my machines I ignore my own advice and pay the consequence of a short hard life ...
I suggest you do the opposite as I spend way too much replacing fried bits.