rico I am going through this myself after having had the AC box replaced about 800 miles ago. craig/derek didn't know what it was, maybe the glues. Some on here have had issues with the pollen filters mildewing. I pulled mine, and albeit filthy, not really a mildew smell...so the only thing I can think is the glues/plastics of the new box. It goes away for me after awhile.
On a side note...I couldn't find the pollen filter listed on the service intervals...some on here have said it hardly needs changing, and I would dispute that. My old rav4 needed it every oil change/10k miles...I will probably do every 10k myself. I am at 20k and this is what mine looked like (at least its an easy change)
Unfortunately this does not appear to be available elsewhere, other than deroure. It turns out it is also a cabin filter for some JCB Farm Tractors, and they're available online for $20 each, but that is about what you pay for the OEM ones. I looked for alternatives, but couldn't find a suitable match for size and the foam gasket.