Personally, I would do some basic tests, trying it with lower intervals first, chances are your CPU or RAM is maxing out.
Try setting the server to be 16 players, see if it crashes, if not, make it 32 players, see if it crashes, and so on and so forth, then if and when it does crash, you'll know you can't run more than that many players on that system.
(You didn't mention how much RAM is in the system, but it could be a RAM issue)
Just give what I mentioned a try, and see if it crashes on a smaller number of players. 128 players is alot IMO, not many servers will get much more than 75 players at once for a while I shouldn't think.
Regards Orpheus