Check you drivers (i know right)
but more importantly.. check for any 3rd party software that manages network bandwidth.
I recently had an issue with AMD Quick Stream regulating my internet like it owned the place... and i installed it in an AMD All in One Driver from my disc that came with my motherboard. uninstalled it and no more problems.
Your a legend! after scrolling through multiple sites looking to find an answer that worked for me i tried this! from 2 m/b down to the 26 m/b i should be getting!!
Many Many thanks.