You might have come to this page as you encoutered same error as mine. I am using Glassmapper as ORM for sitecore.
There are many reasons for this error. Below are couple of them.
Make sure you are passing in right datsource template for your rendering. If your rendering is not expecting any datasource make sure u have datasource field empty on presentation.
If you are in multi-lingual environment, make sure all the items needed by the rendering have this language version, Using language fallback helps in this
