I use XPerl, though I'm not sure it's the culprit with this issue.
I have my main's UI set up the way I want. I see Blizzard's icons for buffs on myself in the upper right of my screen, and I also see buff icons on my player and target frames.
On my alts, I cannot get Blizzard's icons to appear. There is an option in XPerl (current version) to hide or show those buffs. If I toggle it I can get blizzard's buffs to appear for a moment, but they immediately disappear again. WoW's own interfaces option is set to display them, same as my main.
I'm not using any other buff-related addons. I'd rather not throw away my XPerl SavedVariables on those toons and lose all my customizations, but I'll try that as a last resort if I have to.
Any ideas of what could be causing this?