This has to do with the memory allocated to the variables you are using. Somewhere in your program it is trying to convert an integer into a ushort. This is a problem because an integer (also known as int32) takes up way more memory than a ushort (also known as unsigned int16).
An integer can be anything from -2,147,483,648 to 2,147,483,647. Or 32 bytes.
An ushort can be anything from 0 to 65535. Or 16 unsigned bytes (all positive)
So within your program you have an integer that is bigger than 65535. And When you are trying to convert it into a integer your run out of memory. That is the error you are getting.
To fix it, ensure that you do not use any ushort values in your program.
*EDIT: That being said, it looks like there is a problem with your UnityEngine library. I would suggest updating your Unity to the newest one or downloading the EnityEngine namespace for your current one into your Unity folder and replacing the old one.