In order to provide my daughter with an internet connection, I
purchased a Linksys wireless router to transmit my broadband internet
to her computer which is in a bedroom directly above my computer.  It
has worked well for 4 months with occasional unexplained outages of
10 to 30 minutes.  Now however, there has been no connection between
the two computers for two days.  It appears that for some reason, the
wireless signal from the unit in my bedroom is not getting to my
daughter's bedroom directly above mine.  The transmitting unit and the
receiving unit are still in the same location and we can not identify
any additional objects between the two units.  The cable connections
have all been checked and the fact that I still have my internet
connection would indicate that the transmitting unit is getting the
signal and when I unplug and then replug the receiving unit, my
daughter's computer recognizes that activity. Anyone have any ideas
on what may be interfering with that signal transmission?

Have you tried powering down all the computers and the router and
modem providing the connection for a few hours to see if cooling makes
it work again.

To 12345a-ga:  Thanks very much for the comment!  When I shut
everything down overnight, the next morning it worked fine.  Thanks
again.

Do you have a cordless/wireless phone?  Cordless phones can utilize
the same frequency as wireless networks, especially 2.4Ghz phones. 
You may want to jump to a 5Ghz phone if it turns out to be the
culprit.  You can find info here:

http://www.wi-fiplanet.com/tutorials/article.php/2191241

It sounds to me like you need to upgrade your firmware in your router.
Linksys routers generally sit in warehouses for a long time and so the
firmware installed it old and sometime a few versions out of date. If
you don't know how to do this, check out the linksys site for firmware
upgrades for info on your particular router. I guarantee it will make
a huge difference.

I recently got a new wireless laptop, and had similar problems.   I
learned several things:

You REALLY need a laptop cooler if you use the laptop for more than a
few minutes at a time. I noticed the heat would "freeze" my internet
activity, even though I had a connection signal.

As Tarheel suggested, cordless phones are known to interfere. I also
found out, the hard way, that microwaves, washers and dryers can
interfere. Anything with the same frequency can interfere. I've read
that vacuums, fans, and even fish tank filters can interfere with a
wireless LAN!


See Number 16
http://www.zyxel.com/support/supportnote/p652/faq/wireless_faq.htm#16

Good Luck!