Weird underlayment for tile uncovered - what to do???

I'm in the process of repairing the tiles in my kitchen; I've not done a lot of this before but I thought it was going to be a simple job - pull the broken tiles (there's lots of them - probably about 50-60 tiles) and then cement new ones in; scrape everything and re-grout. The house is ~22 years old, the tile was apparently done in the late '80s.
Well, I'm starting to pull the old broken tiles.... but I found this weird underlayment - it's like corrugated orange plastic, with a white (fiberglass?) loose felt and polyethylene mesh on the bottom. It's been set down in a thin layer (~1/4") of a white substance, not thin-set because it's soft, breaking down and really dusty, more like plaster-of-paris. The tiles are set in white thin-set (not like the stuff underneath) on top of the plastic - see these pics (200KB each):
http://img.photobucket.com/albums/v496/ecmcdougall/tile/tile2.jpg
http://img.photobucket.com/albums/v496/ecmcdougall/tile/tile1.jpg The corrugations are about 3/8" deep and 1/2" wide, and the sheets of plastic are about 4' wide (haven't found an end yet, probably came in rolls), overlapped at the edges. I assume this "system" is the reason the tiles are breaking - it looks like an early variant on the modern "waffle" plastic underlayment system, but it's not embedded in thin-set - the corrugations are full of air - so the tile is basically unsupported and breaks.
So, my question is, what do I do??? Does anyone have any experience with this "system", and if so, what is it supposed to be? Can it be salvaged, or should I pull up the whole floor and start again, turning a $100 repair into a $2000-4000 month-long project?
Right now, I'm kind of thinking of cutting out the plastic in 4X6' squares where repairs need to be made, putting down cement-board, and then resetting the tile over that. It won't stop the old tile from breaking, but with the right thickness underlayment it should look fine.
Any suggestions?? Thanks for reading!
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The plastic is used to isolate movement of the subfloor from movement of the tile and tile mud. This prevents cracks and buckling. a few thousand years ago the Romans did the same thing my putting the tile mud on a layer of sand to isolate it from the movement of the underlying structure. Some of those tile jobs are still sound today. It sounds to me like your isolation membrane was set on top of gypsum floor leveler which is what is breaking down. snipped-for-privacy@yahoo.com wrote:

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It could be a uncoupling membrane, like this: http://www.schluter.com/english/products/2002/sectionf/ditra/601-index.html
I bet there is some one at the John Bridge forum that has heard of the stuff you have. You might want to post the same pictures there: http://johnbridge.com/vbulletin/forumdisplay.php?s=&forumid=1
Darrell

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Darrell Dorsey wrote:

Thanks for the replies.
I found a company that installs Shulter products, they said it was the old style (1980's) of the isolation membrane - and the problem is the floor leveler used to put it down. It's supposed to be set in a bed of thin-set, so they recommended removing the entire floor and using a new membrane with the appropriate thin-set.
Not what I wanted to hear.
On the plus side, the tile comes up really easily, I could probably lift the old tiles, sparing as many as possible, and only have to replace the broken tiles. The hard part would be removing the old membrane and the leveler. Then there's the added expense of putting down cement board and fasteners - about $250-300, I guess. Big job but I don't see I have much choice.
Thanks for the help, folks.
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snipped-for-privacy@yahoo.com wrote:

Like was said, an isolation membrane. Seems something wasn't done correctly causing you tiles to crack. As you have surmised, pull it all out and begin again. You may want to assess if you really need such a membrane. Usually you do not. Easiest thing to to would be to rip it ALL out, clean everything down to sub floor. Begin anew. If you have replacement tiles that match the old and can easily remove thinset from those that aren't broken then go for it. Usually the best bet is to start completely new.
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