I suspect something is running in background, such as a worm or virus, maybe some spyware. Or you are under some sort of DOS attack. This would also explain the loss of UDP.
Sudden drops in frame rates are indicative of the CPU being used for something else. Look in the task manager and see what percentage of CPU is being used by Aces High. It should be at 99% or better.
My guess is that the percentage percentage will be lower.