I use HD6750, tried also on 8600GT same result...
really annoying when you are near top speed and your speedometer needle moving slowly, you can see how every new pixel become white...

I guess that means the needle isn't proper geometry which can be antialised by the most common AA techinques.
Super-sampling antialiasing should however smooth it out, but it's quite costy on performance.

run highest card settings then highest game settings.

no improvement ? somethings gone wrong when you tried the above

This may be somewhat off-topic.. anyway, even the overlay-ed (through DirectX) items get filtered...
+1 about something, somewhere, going terribly wrong.