[PowerPC603]

Just add "print"-lines between all lines of code in your OnPlayerSpawn.
After you crashed, checkout which "print"-lines are printed to the server-console.
If you're missing some lines, you will find the problem.

pawn Code:

public OnPlayerSpawn(playerid)
{
     print("Executing OnPlayerSpawn");
     SetPlayerPos(playerid, 100.0, 125.0, 10.0);
     print ("Placed player at 100.0, 125.0, 10.0");
}

Something like this.
If the first line is printed and the second doesn't, you'll see that the problem would be the SetPlayerPos line (in this example).