Hello, ifup-aliases sets up new default routes for each configured [eth tested] interface. It uses GATEWAY from /etc/sysconfig/network for that. Seems to the author of this script just copied stuff from ifup to ifup-aliases Removing all default gateway stuff from ifup-aliases fixes this. Who needs default gw's on each if-alias anyway?
This was fixed in an initscripts release at some point between 6.2 and 7.0.