Hi Kate, I tested on Linux and observed the same error you report with Sparky 3.110 and Chimera 1.2065. I tried a few changes and was not able to make it work. I also tested on Linux Sparky versino 3.112 and Chimera version 1.2154 (as recommended in the Sparky manual) and Model Panel did work. So you could update your versions if it is worth your trouble. Otherwise the best suggestion I can offer is to not use Model Panel. I believe the problem is because a library called Tix is not being properly initialized by another library called Tcl. Tix is needed by Chimera but not by Sparky. There are lines in the Sparky startup script (sparky/bin/sparky) that set variables TIX_LIBRARY and TCLLIBPATH that are supposed to allow Tix to initialize correctly. The only different in the Sparky startup script between 3.110 and 3.112 is that Python 2.4 is used instead of Python 2.3. Chimera may have changed the way it initializes the Tix library. The error occurs in a Sparky file Tix.py that is also included in Chimera. But the Chimera and Sparky versions of Tix.py are identical. The missing tixDisplayStyle command is supposed to be initialized by libtix8.2.so (or on Windows libtix8.2.dll) that is included in Chimera (in chimera/lib). Tom