Dirt 3 FPS drop (multiplayer)

[Rydel95 0]

I bought dirt 3 in the codemasters weekend on steam and i am having issues with the multiplayer.
Everytime i enter the online tab in multiblayer the fps drops alot (from 30 to 5, on the lobby and on the race) making the multiplayer part of the game unplayable. i searched around the web for fixes (forcing directx... read only replays... changing the audio driver...mutting everyone...) but none worked,
so i came here asking for some help, any  would be very apreciated, thank you for your time (sorry for any errors in grammar, english is not my native language)
 

[Rydel95 0]

i rebooted the pc and it came back to normal, i dont know what was causing it