I have never seen the black hole problem, but in my latest 3.03 game I do see a noticeable slowdown during AI turns. For me it's not a problem, but it is noticeably slower than previous versions.

Funny thing for me, I only experience the lag when I click on a black hole, especially if I am moving a ship. If I am moving a ship, the game will lag for about 3 seconds before it will course correct to the next nearest hex that can be occupied. Pre 3.0, there was no lag when doing this.

Have you tried reinstalling your game? Any hardware issues? Do you still get the issue if you reduced the number of players?

I get major speed boost when I decrease the number of players to 10 or less, and I mean all AI turns combined takes like 2-3 seconds when I move the map off screen to skip moving animations.