I have chimera-1.5.3 running on my Linux-AMD64 Ubuntu (12.10) computer. It works fine in every respect. Recently I installed version 1.8, with runs, but with one fatal flaw. By "runs", I mean the chimera screen comes up, the menus display. If I load (say, a pdb file), it seems to be there in the sense, for example, that I can open and view its sequence. BUT the molecule display window is absolutely blank (black). I suspect it has either to do with my python installation, or with my NVIDIA graphics driver. But whatever the problem, it effects only v. 1.8, not v. 1.5.3. For NVIDIA driver I'm using version 310.14. For python, I understand chimera uses 2.7. My python executable is indeed set as version 2.7.3 (that is, `python --version1 returns 2.7.3), though I have version 3 installed, and it could be used, if needed. I'm not all so clear on how envars PYTHONHOME and PYTHONPATH may or may not effect chimera. Of course, the easy way out is to stick with chimera-1.5.3 -- but one likes to stay up-to-date. Thanks in advance for any profound wisdom. Bob Wohlhueter