[WireX]

ok, I am too lazy to read all the replies (missed bout the last 10) but in my experience this is waht is is:

in one word: Calcium (well, in my case anyway)

I ran a pure distilled water setup for 3 months, and when everything got too foggy to see through nicely, I decided to clean the setup (well, the leak helped perswade me too).

When I took off of those, I could clearly see a "White" (not any other colour) buildup. First though, get a CLR rip off. So I ran upstairs, but we only had half a bottol of "Lime-Away" left, but I figured it would work (important later). I filled the tupes, and let them soak for two days, but it only made the tubing 'spotty'. I then looked at the bottol, and it said it only worked on lime, not all three. I then soaked them in hot soapy water, but that only made the spots more visible (not quite sure why). So then I went to the store, and bought 1 liter of Isopropyl alcohol (we were out, and you can never have too much). I ran my whole system with about 500ml of the alchol and whatever it took to top off my system of water (mabe 100ml).
It took two more days, but all the fog is gone, and now I run Anti-freeze, so I will see if that helps at all.

One explination, but may not solve the probolem for all of you.
Btw, I didn't get any foaming... and it was 99% pure stuff, just in case it matters.