[Edit] Forgot to say Win7 x64
Quad Q9550 @ 3.2GHz OC
8800GT with newest 190.38 drivers and previous drivers
The max number of seeds an asteroid can have AND you can still move to it, seems to be 500. If the asteroid has 500 when you try to move, it won't let you. I've noticed this often in the game, as I like to amass huge armies to take over other places. The actual max an asteroid can hold, doesn't seem to be limited by anything other than how many uber-groups you can move to the seed before it reaches that max number of 500.
With that out of the way... I've gotten to the later part of a level and when I try to move any group at all, the game very, very slowly begins sending seeds. I'm not talking about frame-rate issues (though it is a little low too), the seeds simply take forever, or in the worst cases, only send some, stops, then starts sending a few more, and on like that. This happens even when I'm not sending them to the same asteroid. I played one game where I had 4 400-500 armies and I was sending them each to separate planets. Yes, my frame rate was low (in the 20s), but that wouldn't account for the stream of seeds taking forever to decide to go, stopping, then restarting, over and over. I even have a video of one time I did it, just because it seemed so weird.
Once it lost me a game
. It's usually no deal breaker, but it can be extremely annoying when you are trying to make simultaneous strikes on the same/different planets.
As for the other instance, the clutter lines, I have also seen them too. As a matter of fact, I have a video that captures the lines too. Mine flash on the screen when scrolling in/out in the later game when there are lots of seeds around. Attached is a pictures of the lines.