Problem with signal strength

I have a Dell Truemobile wireless router 802.11g, and a Dell Truemoble
wireless PCMCIA card for my laptop. I have had it set up for about a year
with good connection.

I just moved and also just bought a 900 MHz cordless phone, and now I'm
having problems. At first, I couldn't connect at all. I called Dell tech
support, and they had me change the channel from 6 to 11, and now I can
connect. However, the signal strength keeps fluctuating between Low and Good
or Very Good. Sometimes I get an Excellent. But it fluctuates every few
seconds between the two, and my Internet connectivity has been intermittent,
as well.

I've tried turning off my cordless phone, but that doesn't seem to make a
difference. So I'm thinking that maybe my neighbor has a 2.4 GHz cordless
phone or something like that. Anyway, right now I'm sitting right next to
the router with my laptop, and it's still fluctuating between Low and
Excellent, so something's not right. I used to just get a solid Excellent or
at least Very Good. There must be some interference somewhere, it seems.

I'm wondering if I should try another channel or if there's something else I
could do to resolve this.

Thanks for any assistance.

Neil