gnome fails after gdm login

This seems similar but not quite the same as previously reported bugs.
After upgrade to Intrepid RC from Hardy, gdm performs normally, however I then go to either a black or brown (no clear reproducibility of the color difference) screen with a pointer that I can move, but cannot do anything else. Cannot ctrl-alt-F1 to shell, or ctrl-alt-bckspce. Xorg.conf seems fine (and I don't think the problem is related to X as I eventually installed fluxbox, which works normally -- including gnome apps!). This seems most similar to bug 259385, except the compiz remove/compiz-core remove doesn't help.
I burned a LiveCD, and it was ok live, but same problem after install.

System: Dell 4300s with standard intel P4 2gHz, 750 RAM, Intel VGA 82845G/GL[Brookdale-G]/GE Chipset Integrated Graphics, Realtek ethernet