My Mac laptop isn't "connecting" to my wifi?

[Pumped Up Kicks]

The wifi is working--my sister can access the internet on her laptop (which is a few years older than mine; I just bought mine a few months ago), but I can't. My computer shows that the wifi is up and running, and even "connects" to it, but I can't access the internet or send/receive email.

I can' connect just fine to other networks like in Starbucks and at school, but not at home. The power went out a few days ago, and our service provider had some trouble (so it wasn't just a problem on our end). But when they finally fixed it, my sister got access and I couldn't.

I've reset my computer's network settings, restarted my computer, restarted the modem/router, and even tried connecting my computer directly via cable.
Nothing worked!
I need the internet for school.

What could the problem be??

[Bob]

Here is all the mac and apple help in one place... Hello, Ask Apple here for free 1-800-MY-Apple ,and check out the sites for more informaton http://www.apple.com/support/ and
https://discussions.apple.com/thread/246...0&tstart=0
http://www.facebook.com/pages/TheAppleGossip/...
http://www.apple.com/macosx/recovery/
http://9to5mac.com/
http://appleid.apple.com
http://www.apple.com/support/mac/facetime/
http://www.ifixit.com/iPad-Parts and Mac parts
http://www.apple.com/iphone/built-in-app...phone.html
Hey, I enjoyed your question, I have worked as a technician most of my life, I
hope I have helped you...
Good luck...

CompTIA A+ Certified Computer Professional