Prior to version 1.10, 2d Toolkit went through your project and loaded all prefabs to find 2d Toolkit objects. As you can imagine, this can be a very slow and memory hungry process when you have a large number of prefabs. 2d Toolkit 1.10 creates an index of all your 2d Toolkit objects the first time you use it. Version 1.10 uses significantly less memory. We recommend you upgrade to the latest version as soon as you can.