I noticed that there's an article on ethernet jacks on appledefects.com
After a bit of research it appears that several of the issues with the MBP are caused by the overheating. Such as the airport lost packets etc.
What prompted this research was a freeze due to overheat (watching DVD I did notice it get hot with a GPU temp of 68degC!).
So I'm tempted to reapply the thermal paste.