1) Crashing in later stages of a game... especially on Large or Huge Maps vs more than 4 AI opponents
2) Mines... if there's too many in a solar system (Eg: Vasari AI opponents seem to like to completely envelope a planet) and you take a large fleet to overtake it, it blanks out many units and mines (not visible) as it doesn't seem to be able to display them all.
3) Vasari AI opponents with Ruiners simply create too many mines around a planet. This leads to minidump crashes every time...
4) Need a better way to remove mines. Currently unless you constantly babysit your fleet and keep them away while your seekers fly in close so your bombers can destroy them, both your fleet and the seekers like to simply run into them. Which brings me to my next point...
5) Seeker/Scout vessels need to lead the fleet formation not wind up near the back or middle.