I encountered the same problems when I upgraded to Fedora Core 6.
I tried different combinations of AOLServer 4.0.10, 4.5.x, from CVS and tcl <= 8.4.6, 8.4.13, .14, CVS but never got xowiki working and got intermittent server crashes.
Here's how I solved it:
- Downgraded bash (FC6 comes with bash-3.1, I downloaded the bash-3.0.x source, compiled it, symlinked /bin/sh to the compiled bash binary)
- Used tcl-8.4.6 instead of tcl-8.4.13 that comes with FC6 (it's unfortunate coz the tcl in FC6 already has threads enabled)
Now everything works perfectly with aolserver-4.0.10, xotcl-1.5.2 and the latest xowiki and xotcl-core from HEAD.