what is wrong with my wireless? consistent "scanning..." on strong signal

Fairly new to Macs, just switched this summer. I haven't really had any troubles, but recently something is getting annoying.

My wireless connection has suddenly gone to crap. Airport constantly says it is scanning and my connection is maintained but doesn't work. Now I know that the natural inclination here is to blame the router, but:
A. I have two different wireless networks with full signal available to me, and it does the same thing with both
B. Something about the connection is weird, because last night I was able to download something at 200+ kpbs and use an instant messaging program, but Firefox got nothing.

I wondered if it wasn't a Firefox thing, but then why would Airport be scanning all the time? And what does "scanning" mean from that anyway?

I just want my internet to work consistently again!

fyi: Referring to Airport in the sense that "AirPort: Scanning..." is the message I keep getting. I don't know what the routers are... I know one is a Belkin, not sure about the other. They are both in adjacent apartments so I can't reset them, although I can call and ask to have that done if necessary.
15" MBP, 4GB RAM, Mac OS X 10.5.5

 

Good to know. Doesn't help the fact that my internet isn't really working most of the time, though... I'm just really boggled by the fact that it probably isn't the router (since both networks are doing the same thing).