Okay, I got the problem resolved in the following way (thanks go to Clint Leysath):
1. removed the tcltk++ directory that came with my ccp4 download 2. installed Activestate's tcltk 8.4.19.2 from https://www.activestate.com/activetcl/downloads/ 3. downloaded blt2.4z.tar.gz and the blt2.4z-patch-2 from http://sourceforge.net/projects/blt/files/ 4. unpacked blt2.4z.tar.gz and moved the patch file into the blt2.4z directory 5. patched the blt installation (patch -p1 -i blt2.4z-patch-2) 6. then reordered statements in blt2.4z/src/bltTree.c [this is detailed at http://www.ccp4.ac.uk/ccp4i/install_tcltkblt.html under the heading Compilation failure in bltTree on 64-bit machines] 7. configured the blt install (./configure --with-tcl=/path/to/ActiveTcl-8.4) 8. installed blt (make) 9. for some reason bltwish did not end up in /path/to/ActiveTcl-8.4/bin even though the configure script said that is where it would be put, so I moved it to /path/to/ActiveTcl-8.4/bin 10. edited 1 line in ccp4.setup-bash (setenv CCP4I_TCLTK /path/to/ActiveTcl-8.4/bin/) 11. opened a new terminal window & ccp4i works
