Just wanted to post this for anyone finding this thread in the future...
I ran into this error today while installing OpenACS 5.2.3 on a Solaris 10 system at work.
It turned out that /var/tmp was owned by root and only root had write permission (!?). The Tcl core (in tclPipe.c) needs to create a temporary file to use as a sink for the stderr output for the pipeline. The "couldn't create error file for command" message was being generated by [open "|..."].
After chmod a+tw /var/tmp and restarting I'm able to proceed with the installation.
Now I'm able to proceed with the installation.
