If your map is large and contains a lot of entities, chances are you'll run into the 'ED_alloc: no free edicts' error. This error means that there are no more free slots to load entities into. By default there are (only) 900 free slots but there are ways to increase this limit.
You can add a launch parameter to your game:
This will increase the limit to 1500 slots and most likely solve your problem. However, this creates a problem with the shipping of your MOD, since you'll have to instruct everyone to manually add this line. Luckely, there is a better way to do this:
In your MODs root directory there is a file called 'liblist.gam'. Open it with Notepad and add the following line:
This file is shipped by default with your MOD, so it will prevent possible problems with players who do not know how to use launch parameters.
Some sources claim you can add infinite amount of slots with these command lines, but I'd advice not to use more than your map really needs. You should probably not set it higher than 2048, since that is the limit of the entity index. Creating more than 2048 entities will most likely crash the game.