How to fix negative ping times on AMD dual-core CPUs
Problem: When using ping or tracert on dual-core AMD CPUs such as the AMD64 X2 on Windows you may see millisecond counts above 4,000,000,000, which are negative 32-bit numbers displayed as unsigned.
This problem shows up on the AMD64 dual-core CPUs because the power management may slow down or otherwise put to sleep one of the CPU cores when load is low to save power. This causes low-level counters to get out of sync between the two cores. If an application reads those low level counts in order to measure short intervals and gets run on alternate cores, the return values become erratic and may appear to go back in time.
Install the a fix called "AMD Dual-Core Optimizer" from the AMD website. Note that you will have to reboot your machine to activate it.
ljackson.us article on the problem