A couple of things my wife has suggested (she's the computer guru at my house and has the certifications to prove it):
Have you bought a new wireless phone lately? That could mess with the signal.
When was the last time you rebooted the router? Should reboot it every other month or so.
Check to see if anyone's pirating off your connection. You'll have to go into the router to check.
Make sure broadcast is turned on in the router.
She doesn't think it's the card. She says typically they just flat go out. They don't do what you're describing when they are bad.
Hope that helps.
Yes doctor, I am sick.
Sick of those who are spineless.
Sick of those who feel self-entitled.
Sick of those who are hypocrites.
Yes doctor, an army is forming.
Yes doctor, there will be a war.
Yes doctor, there will be blood.....