Hi Siebe,
Sorry for the trouble. I agree with Robert's suggestion to check whether "Wat" might be causing the problem.
The CIF Browser and Feff runner in XAS Viewer does actually support fractional occupancies, by randomly assigning atoms to match the partial occupancy (but of course, not with great precision -- each X, Y, Z position has exactly one actual atom of a determinant Z). That allows a lot CIF files to "just work" that would otherwise need manual intervention. At the moment (and possibly for the foreseeable future), the CIF Browser does not support editing the CIF directly, but does support editing the result Feff.inp file, but one can export a CIF, edit that elsewhere, and then import it.
What I see trying to run a calculation from that CIF file is that there are many oxygen atoms that are too close together. Like Robert suggested, I suspected these come from the "Wat", but when I removed those and the H atoms, the prolem still happened. As Robert listed the atomic positions for this structure, I think it might actually be the "C", "O2", as well as the "Wat" with the low occupancy of "0.0833" that might be the problem.
If I remove CO groups and Waters, these to generate the attached CIF (I changed the ID number) that seems to run, though I don't know if it is then the structure you actually are trying to model ;).
--Matt