By default, MC is set up to "Replace Playing Now (all)" when you double click. That means that if you are in a view that shows 1000 files and you double click one of them, ALL 1000 files will be put into Playing Now, replacing what was already there.
If instead you drill down into a single album, with just the tracks from one album showing, then when you click on one file, only the files from that album will replace Playing Now. It's all about what is *visible* when you double click a file.
Personally, I don't like the "replace" behavior and I really don't like that it takes "all" files. So I've changed the default to "Add to Playing Now (play now)". This probably won't help you though, as that just applies to a single file. If you want to be really precise, highlight the tracks from the album, right click, and select play. That will definitely work every time. Get to know how MC uses the Playing Now queue: It's a really powerful system.
Finally, you can choose from several behaviors for what a double click does. Check out the options at:
Tools > Options > General > Behavior > Double Click
Good luck.
Brian.
