Well...most of the time I save my parks 4 times a ''month'', and before I hack something and after the hack is complete, so I think that is not the problem. I already made a back up file with 'only' the 4 black holes, so I think I will just continue working on the entry and hope they diappear. But the most annoying thing is: it is exacly at the edge of a buiding, the biggest building in the park.
Thanks for the help!
Luigi
Edit:
It worked

now there is only on left, so at least I can repair my building now.
At one moment I thought the whole game was going crazy, I had to 'cap land at max height' 4 times at the places of the holes, really strange and after that the 3 were gone
little *******...10000 times thanks for the advice!
Edited by Luigi, 22 January 2008 - 11:19 AM.