Driver problems

[Discospawn]

Hello
My computer isn't working properly, when I installed the latest drivers for my 4870.
Everything went to so much better except when I want to watch film. Somehow without drivers I could
watch my movies, but now my graphic card does not seem to manage it. Every sec 2 frames is white.
I can still see what happens but it's quite annoying to have an flashing inferno in front of your eyes for
whatever length the film is.

Also my internet seem to work when it feels to be kind. But if it works in bootup it will work til I shut it down.
And it maybe works the next time I start it.
I have no router or modem, directly into the wall socket.
My motherboard is GIGABYTE ep45-ds3.
Bad drivers?

Thanks

[Husse]

Which version of Mint? - exactly
What is 4870? Radeon?
What do you mean by
Also my internet seem to work when it feels to be kind.