OLN stands for object limit number so the title should read OLN fix? Anywho, I beleive there is a method were you use the default objective items, delete them and it frees up some OLN. Then save and start up again, repeat the process. I heard that worked but im not quite sure myself, worth a try tough.
There once was a way to do it. They even had a tutorial of it on the forging 101 sub-forum. I'm not sure if it's still there though because it didn't really work and even if you were able to break the OLN and create more objects, it would be considerably laggy. So all in all it's not worth it. You'll just be stuck with a really good map that nobody wants to play on because of the intence lag. I hope I've helped out a bit. xX BtR Chaos Xx