Well, it worked as it should for a time. Yesterday it went berserk :huh:
I have noticed that this massive problem is present since beta (Autumn 2010)... Jiminy Cricket!
On a side note, I think I've found a workaround: During the runway start, just speed up (LCTRL + Y) for ten seconds, then set it back to normal, and it sorta works.
Note: DCS A-10C Warthog, mission 'Shooting Gallery.'