Altium 17 somehow lost shortcuts, I cannot rotate a part with the spacebar
I am using 18 now (which might be wise to update to) but I thought I remember stumbling over this as well. If I remember correctly you have to click on the component and then rotate, not click and hold and then try and rotate within Schematics.

Whereas, in the PCB docs you have to click and hold and then hit space bar in order to rotate the component. 

I see 17 is different then 18 but this shows how to get to the shortcut menu and reassign keys. 
https://www.altium.com/documentation/17.0/display/ADES/Altium+Designer+-+((Shortcut+Keys)) 

Also, you could reset your preferences in the preferences dialog and see if that helps as well. 

Ultimately, I would recommend moving to 18 as it has some pretty cool features and then all the documents are easy to reference.