I invested in R.H. Donnelley a few years back (I'm still kicking myself for that mistake... ) and they eventually filed for bankruptcy. Just this month the Company announced it has emerged from its Chapter 11 restructuring as Dex One Corporation. So does that mean my stock in R.H. Donnelley is now worthless and isn't associated with Dex One? I would appreciate any answers.

According to the Dex One website it seems that all old stock holders of RH Donneley were wiped out. The new DEX stock was distributed to bond holders only only. See:
Dex One Corporation

You may want to call the Dex investor relations department to confirm that tytis is correct.