Had this problem with one string set a while back. When I re-stringed after they broke, the harmonics came in perfectly. Just re-stringed again, and now they won't sound anymore. Twelfth fret harmonic and twelfth fret note sound the same (I heard that's a means of checking intonation).

Any ideas? Too angry to use good grammar.
"Optimism," said Cacambo, "what is that?"
"Alas!" replied Candide, "it is the obstinacy of maintaining that everything is best when it is worst."
mybe u have to ajust your action?
Quote by KGB_INC
none. i've never had sex.
probably never will.

My Gear:
B.C Rich Warlock
32 year old antique yamaha accustic
Peavey Ovation
Peavey Millenium Bxp 5 string Bass
2000 Watt Peavey PA system
Line 6 Floor Pod
What guitar do you have?
Schecter Hellraiser C-1 Fr
Gibson Les Paul Studio with Seymour Duncans
Avalon Gold series acoustic
ESP LTD 7-string

Marshall 100DFX
Peavey Valveking 212

Boss GT-10
If you changed gauges when you re-strung your guitar the action may be too low. For good squeals your action does need to be set a few thousandths high.
I love all 5 (sold a couple) of my Carvin X-100b's.