CentOS - May 2007 - OT? Alt-tab flashes differently between work and home

This may be off topic, but I'm not sure where to go - been to Gnome
help and google - nada (wrong search?).

I have CentOS 5 on both my work and home machines, with Gnome 2.16.0
(default, straight out of the box, so to speak).  At work I have two
17" FP monitors on an ATI FireGL V3400, at home I have one 19" CRT on
an nVidia GeForce7100gs.

When I use alt-tab to switch windows at work, the border of the window
that is the current target of the switch flashes black - this is fine.
 At home, the whole window goes black.  I'd like to change this to
flash just the border at home, but . . . how?

I've tried looking around for a setting for this and I can't find one,
but I'm stabbing in the dark - even google doesn't give me anything,
although the searches I've tried might have been off-base.

Any suggestions?

-- 
Mark Hull-Richter
DATAllegro (www.datallegro.com)
85 Enterprise, Second Floor, Aliso Viejo, CA  92656
949-680-3082 - Office     949-330-7691 - fax