Pointers and crashing

Alright. The Program is running along on its merry way until it hits: PtrMap = new _Map *[NumX]; // // Make a 2 for( int x = 0; x < NumY; x++ ) //Dimensional Map[x] = new _Map[NumX]; //array //dynamically When it gets to the fourth time it hangs/crashes. In windows it gives a "MS-DOS program has performed an illegal operation and will be terminated..." What the heck? It cant be a memory problem (i think) because I restarted my computer and tried again. Any insight?