Yeah, Roger answered the problem directly. Snowmelt has all sorts of dust, pollen, spores, etc in it. Even the mineral deposits left by differing waters can leave strange tasts if overheated.
Most "Ti" pots are an alloy of aluminum and titanium. Most produce various oxides when exposed to air, or even the disolved air in snow. Acid has a real bad effect on Aluminum pots and pans in general. They often leave a tinny taste. I almost always use Aluminum simply because there is no pots of the same capacity I can use for camping. 3.25oz including a top for a 1L capacity is light. I have used ti, and the bubbles and localized heating of the mineral scales can easily exceede 100C. Mostly the oxides from ti are flavorless and not very soluable in water. Same for Aluminum. Acids can change that with Aluminum, not so much with ti. Both can suffer local overheating from mineral scales.
Anyway, here is a pretty good reference on ti and it's oxides.
http://www.keytometals.com/article24.htm It has a good overview on ti and it's oxides. Note that mostly, this looks at pure titanium, not the typical alloy in use for pots.
Aluminum is a better conductor of heat. Generally there is little measurable difference between camping pots, though, usually ~3%, per Rogers figures. You have to have a pretty good set up to see any difference. I am guessing this is due to the aluminum component. Heat exchangers can be added to aluminum pots. Not so much with ti, since they really need high heats to work with the metal. This can add about 15% more efficient heat transfers for a typical aluminum pot. With ti, this isn't feasable for most of us. You need a press and a set of dies, really, to do ti stuff.