Just a heads up to those out there that may run into this problem.
Problem: Scalix installer will report failure on system check of "network" and "running services". However, it will not report the error in the GUI log details.
Reason: When installing Scalix and running under a user account that you have used to "su" to root, be aware that by default "/sbin" is NOT in your path (at least in my case ;)). The installer uses chkconfig and ifconfig to determine network settings and running services.
Solution: What I did was add /sbin to PATH in .bash_profile, logged out/in, su'ed and everything went fine.
I checked /var/log/ for the scalix log to discover the problem. I don't know if this is in the KB, but if it isn't I hope it saves some poor soul a bit of time :)