This is probably a bit late, but anyway, tracker-store is part of tracker, a program that scans certain specified locations on your hard drive (and other places like your emails) and indexes the contents into a database. This allows you to do fast file contents searches. To the best of my knowledge, tracker-miner-* are programs that scan data and tracker-store is the program that stores the metadata in a database for fast access later. Tracker uses a database for its own purposes, so it makes sense that it can use your CPU even when you are not dealing with RDB access yourself.
To be clear, under normal operation, tracker should not have excessive CPU requirements as it should be IO bounded, not CPU bounded. However, I too have had issues with tracker doing what you describe, particularly on login and X startup. A little searching found
this (for MeeGo, I didn't know they used X).
To solve your problem in the short term, look over the suggestions in the link. You could also configure tracker to index nothing (see program tracker-preferences), thereby probably stopping it from doing any work at all. Or you could try removing the package entirely, but I'm not sure if that would break anything or not.
