The if-up and if-down scripts do not work for ip aliases under 2.2.x in RHL5.2. I upgraded all the appropriate packages for using kernel 2.2.x under RHL5.2, and it still didn't work. The /etc/rc.d/init.d/network script reported that device aliasing wasn't supported by the kernel. It was, and I brought the alias up manually with ifconfig. I ended up writing my own initscript and alias-up/down scripts, but it is a cheap hack and I think it could be taken care of better.
what happens if you comment out the portion of the initscripts that refer to linuxconf?
what does ifcfg-eth* say?