A friend asked me for advice on how to speed up the loading of web
sites on her computer's browser. She said that ever since hooking up a
third TV to her Time-Warner cable service, her computer, which is
connected to the same service (Roadrunner), had been behaving
sluggishly. When Time-Warner's cable techie looked at her setup and
tested the signal strength at her computer, he concluded the third TV
was indeed the culprit and attached some sort of signal booster near
the computer, though the booster seems to have had no effect. I
suggested she unscrew the cable from the third TV, and, sure enough,
her computer immediately began to perform acceptably. That said,
she'll now have to leave one TV unhooked whenever using the computer.

This was the first time I'd ever heard of this issue. Have any of you
ever experienced the same, and, if so, how did you resolve it?

if the cables are being split from a 3-way splitter (1 in from the
wall --- 3 out to the tv, modem, etc.) the signal will definitely
become weaker. If your friend has a 2-way splitter and is then
splitting it again into 2 (1 splitter into 2 then one of those into 2)
then the signal will be terrible. If she really needs the two TVs, she
should get a something like
this:(http://www.shop.com/op/~ULTRALINK_PRO_3_3_Way_Videophile(R)_Ultra_High_Performance_2_GHz_Signal_Splitter-prod-14889693)
or a similar device (http://froogle.google.com/froogle?q=Bidirectional+Cable+TV+Amplifier&btnG=Search+Froogle&lmode=online&sa=N&lnk=next&start=30),
I also advise her to contact TimeWarner before making investing any
money in this.