Dear Greta, I have the same problem when working with PowerPivot.
I'm designing a chart, adding the first bar diagram, no problem, adding the second bar diagram, and when I hover the pointer over it, everything disappears.
After that when I click on PowerView icon, error.
If I restart Excel the PowerView, PowerPivot, PowerQuery tabs are gone. Going to Option, COM components, those are checked. After unchecking, OK, checking, OK, those are coming back.
I'm using Windows 7 32 bit and Office 2013 ProPlus 32 bit.
I suppose the problem is with the 32 bit version, I don't have it in the 64 bit version.
Let me know if you now about any patch which can solve this.
I have the latest updates installed of course.
The issue is really persistent.
Kind regards,
Mihly