That's an odd one. As the previous poster indicates, it's nigh impossible to taste cigar adhesive. Is it possible that your humidor was exposed to chemicals, e.g., did you lay carpet or paint the walls recently? Cigars do tend to pick up ambient contaminants from the air.

I had a cigar that tasted fine but then suddenly started tasting like cardboard, whereupon I discovered that I was smoking the label (SWI)