Another wireless connection/IP problem...I think

Ok I really need help. I know these questions pop up a lot and I've looked through everything to try to figure out how to fix my problem but it's hard because the specifics are different and I'm not a computer whiz.

In my home we have a wireless router. My sister's computer is connected directly, my parents' computer connects to the wireless, and my computer used to connect with no problem. My power chord broke about a month ago so I couldn't use my laptop (TOSHIBA Satellite A205-S5000 - Windows Vista) because the battery was drained. We recently fixed my power chord and I was thrilled to be able to start using my computer again. The only problem...it won't connect to our wireless network anymore. I click on "connect to a network" opening the corresponding window. Our wireless network connection is called dlink. It says that my signal strength is excellent. I try to connect and it says there is a problem and I'm prompted to diagnose it. It comes up with the option "click for information on troubleshooting low wireless signal". I'm very confused and I've been fighting with this for probably 2 weeks. I could really use some help. I'm sorry for not really knowing much about all of this. Please be patient with me. Thanks!