This is one of the problems that comes from setting ceramic tile over vinyl. If the vinyl is cushioned you can expect the rest of the floor to follow suit unless ...
TileguybobMember since 07/03/05
Simply put , rip it all out! You can rent a mechaical floor scraper that will get the vinyl up very quickly.
Dont use mastic around a fireplace. It will turn brittle if the heat gets to it causing the pieces to fall off the wall or at least sit there with only the grout ...