Jim,
As far as I've been able to determine, the tclsh which is called has to be able to find the libxotcl thing. Apparantly, not every tclsh I have is able to do that, so I looked closely at the SC_PROG_TCLSH macro (having traced the problem down to that macro) and noticed that it doesn't try to use the tclsh specified in the supplied tclConfig.sh, which as far as I know is the only correct choice (should use the tclsh linked to the same libs that were used in the build process of xotcl, and that can find the modules).
This is not correct, and indicates a problem elsewhere in the xotcl make/test stuff. I see that it still uses the older TEA stuff though, which might be the core problem (SC_* macros were done away with a couple of years ago).
The TEA_PROG_TCLSH looks at TCL_BIN_DIR (specified in tclConfig.sh), then the exec_prefix, prefix, and finally the regular path. This is the right ordering, as it is better to find the installed version first. It's still based off the tclConfig.sh.
Jeff Hobbs, The Tcl Guy http://www.ActiveState.com/, a division of Sophos