Gamer, what operating system are u running? It could mean the hack is patched, or maybe try using a different injector. Also some hacks have a small info box that pops up during/after injection, requiring you to press "OK" or "Yes" to close the box, and in most cases, i think, it won't inject properly if you don't.
I'm using Vista 32 and I get nearly all of mine to work, so maybe i can help you. If not, there are many users here that know a lot more than I do.
I've also found that simply trying again and again, sometimes restarting helps, gets them to work as well. I recommend using FreedomPeace's Portal injector, it's super easy to learn and is by far my fav injector.
Good Luck!