The Content plugin - jDownloads 3.1.2 Beta is only for the jDownloads 1.9.2 Series, and on Joomla 3.1
You need to remove the plugin.
As yet the Content plugin has not been upgraded for the jDownloads j25 or j32 series - it is on the to do list. First objective however is to get the Component stable.
Your next question is no doubt "When?". That is like asking how long is a piece of string, to which the only answer I have ever found is "twice as long as half of it". Basically as soon as possible. There are perhaps three or four significant issues remaining in the component that are high on the 'hit list'.