Strange wifi problem...please help!!!!

Hi guys, i am experiencing a very odd problem and i am completely stumped. I am hoping that someone might be able to help me. This is my first post so please forgive me if i leave out important information. Here it goes:

2 days ago, i upgraded my internet from verizon DSL to verizon fios. o problem here. The technician came to my house, helped set everything up, etc. All was well, and all 3 of my computers could connect to the network and access the internet.

This morning however, i took one of my computers and it could not connect to the router. Even when i attached it via LAN, it still could not connect. All of my other computers still work fine, and the one that is having issues can connect to my neighbors internet without any issues. I have WEP, but have tried turning it off and switching it to WPA thinking that it was the culprit. MAC filtering is off.

Has anybody seen anything like this? Can anyone help? Thanks a lot!!!