I don't know for sure how it works for Poland but I think that acquiring a different citizenship under certain circumstances means that you lose the other one (this used to be the case for Italian citizenship so consulates will require proof that your ancestor didn't naturalize when recognizing descendant's citizenship).

From the site of the Polish Consulate in NY you can find more details... http://www.polishconsulateny.org/en/...tizenship.html
If a Polish citizen became naturalized between 1918 and 1951 he/she would automatically lose his/her nationality.

Good luck investigating!