wireless router problems with optimumo nline

I created a wireless home network about a year ago between my acer desktop
(win 98) and my toshiba laptop (win xp pro). I did not have an ethernet card
in my desktop so I used a Linksys USB wireless adaptor. I hardwired my
Motorola surfboard modem (provided by optimum online) via ethernet cable to a
Linksys wireless router/hub. The toshiba had a compatible built-in wireless
card. It worked okay for a short while then I had trouble getting internet
access with the desktop. I could surf the web AND access the acer's files and
printers on the toshiba without any problems. Only when I reconnected the
desktop directly to the modem (no wireless adaptor or route/hub connected)
could it access the web. I ran the setup with the original configuration,
using the laptop only, for about a year. Last week I lost the toshiba's
ability to access the acer. This is where - probably inadvisedly - I started
tweaking things (sorry I can't remember exactly what I did). One of the
problems is that my ISP - Optimum Online - offers no support for the wireless
set-up. Finally I lost all connectivity and now I get the following message
on the acer "TCP/IP TRANSPORT NOT INSTALLED". The toshiba now has internet
access only when hardwired (ethernet cable) directly to the modem. I was told
by the last Optimum tech I spoke to that the acer probably has a DNS error
(which they do not support). I have no support for either machine and Linksys
has not been very helpful. I guess I am looking for 2 things - 1:any easy
repairs for the TCP/IP problem and 2:does the DNS error sound like a correct
diagnosis?
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all help greatly appreciated !