Your original post is a timely one for me; I'm experiencing a similar thing over the past week or two.
Three months ago I bought an assortment of house blends from a brick and mortar. All were decent blends (likely Sutliff) except one, which tasted to me exactly like new, clean cardboard. (If you've ever worked a stocking position in a warehouse or store you'll know the smell.) The taste wasn't particularly bad or good, it was just...cardboard. I put that blend away and left it untouched since then.
I smoke many different blends but prefer stronger, funkier tastes. Last week I lit up a regular favorite and noticed immediately that it had a hint of that same cardboard taste. Over the next couple of days all of my blends began taking on this same taste. Doesn't matter the moisture level, the way they're stored, how old they are, packing methods, etc...everything is starting to taste like it's about 20% cardboard.
My best guess is I've overloaded my palate/olfactory system by hitting it hard with a lot of potent flavors. It doesn't help that I'm a daily cigarette smoker as well. I'm taking a break from smoking pipes (and probably the cigs too) to see if anything changes. I'll let you know what happens.
I know of only one other person this has happened to, except his "ghost taste" was soap. He said after a month of smoking only Prince Albert (a basic, non-abrasive blend with minimal potency) his palate "reset" to normal. Might be food for thought.