I've had ubuntu for a couple of months and everything was perfect. But then, randomly, my computer would not connect to the internet unless I use an Ethernet cable. Can someone help me fix this?

Computer: Toshiba Satellite L305-S5947
Wireless Card: AR5001 Wireless Network Adapter (made from Atheros)
Wireless Card Kernel Modules: ath5k




*And if you can, make it as simple as possible to understand*