It should work fine. When you say "desktop or laptop" I assume you're using a wired connection for the desktop and wireless for the laptop, and you're having a problem with both? If it were just wireless I'd suspect signal issues, either a weak signal from the router (it's far away perhaps) or interference from a neighbor's router.
Is it just AIM causing problems? How's the performance on the web?
Did everything work fine before you got the router? Does taking it out make things better?
You'd need to do some troubleshooting and see what works and what doesn't. You may need to contact your DSL provider or the router provider, or both. But my guess based on what you've already said is that there's a connectivity problem, or a configuration problem, with the router that is making it not work properly.