Sorry, that is pure nonsense. E1513 is a script crash. This has nothing to do with too much texture memory, to many entities or somehting like this.
A function of your script crashed. The usual suspects are accessing an empty pointer, dividing by 0, or trying to do something with a nonexistent object. Crash errors are only indicated in the development engine. The distributable version will not issue an error message, but just try to recover from the error, and if this is not possible, exit the program. The name of the erroneous function is displayed, followed by the 3-character sys_marker, so the error should be easy to find in your script. If you get a crash right at startup or level loading, a damaged sound, image, or model file might be the reason. Another possible reason is a wrong setting of the DEP (Data Execution Prevention) in your Windows system configuration that prevents running scripts.
Remove parts of your script and see if the error is still happening. If removal of a certain piece of script fixed it you know you have to look into that piece. While at start you should remove larger pieces over time you can narrow down your search scope.
