Dear Chimera team, I do have a question regarding differences between OSes. Our group recently encountered a problem in the surface creation of proteins, which might be related to the OS. Recently, for some structures, directly obtained from the PDB (e.g. 6GB5, 1H97, 4YLJ) or prepared single-chain structures for docking runs, the surface creation of the proteins resulted in error 5 from mscalc.exe. This, however, seems to be an isolated problem of the Windows versions of ucsf chimera 1.12-1.13.1, as the same versions of chimera on macOS or Linux (Lubuntu) could successfully create these surfaces. Even more strangely, we are pretty sure that we could show surfaces of the very same files about half a year ago with these versions (1.12 and 1.13rc1). Did a recent update of Windows change the behavior of chimera? ChimeraX could actually show these surfaces on Windows, but gave us some other troubles. We did have a look at http://www.cgl.ucsf.edu/pipermail/chimera-users/2016-November/012874.html which did solve our problem for now, but we would like to know whether we can improve the reliability of chimera's functions, aside from tips mentioned in http://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/surfprobs.html. An older post (http://www.cgl.ucsf.edu/pipermail/chimera-users/2010-December/005805.html) indicates that it is a numerical problem, is this still the case and means that it is indeed OS-dependent? Thank you in advance, Marco -- Marco J. Müller PhD student Technische Universität Braunschweig Institute of Medicinal and Pharmaceutical Chemistry https://www.tu-bs.de/pharmchem Beethovenstr. 55 | 38106 Braunschweig | Germany