Can anybody explain this anomaly?

[Stryker1013]

I have a computer in a basement connected to a network through a wireless-G Buffalo Airstation. Its worked just fine for almost a year, but just recently I'm getting a really strange signal, spiking from 0%-100% within a second. When this happens, there's no apparent activity when I try browsing, however the computer doesn't report the signal as limited or gone. I can temporarily fix the problem by using the AOSS function on the airstation or unplugging it, but this anomaly comes back every now and then. Does anybody know what this is about?

[Stryker1013]

This is what the network connection graph looks like when the spiking occurs. Notice the range is 0%-100% unlike the typical 0%-1%.