The tablet shipped brand new with Windows 8.1, so I would assume the drivers and DirectX are up to date. Setting warn_level had no effect.
Interestingly enough, plugging in the keyboard unit (which essentially converts it into a small laptop) not only removes the error but fixes the non-working mouse click events as well.
Unfortunately, we want it to work as a standalone tablet, so this isn't really a proper fix in the long run.
@Ch40zzC0d3r: Interesting thought. How would I accomplish this?