Something started a local network, please help

Hello, I do not have access to DSL or cable high speed, so I run a Sprint broadband card (EVDO) plugged into an iBook G3 set to share with a MacBook and a Dell laptop. It has worked flawlessly for the past two years--until last night. It worked fine all day yesterday, then I partially installed Missing Sync. I couldn't complete the installation because I had to leave, so I stopped it at a logical place to pick up later. I later used the MacBook with the broadband card at a different location (no sharing), then last night when I came back home, I again put the broadband card back into the iBook, and when I tried to connect with the MacBook, there was this Apache page ("installation of the Apache web server was successful"). It was terrible after that--although the computers said they were connected (both the Dell and the MacBook), they wouldn't log onto websites. Each computer worked alone when the broadband card was plugged in, but no sharing at all. Finally, I went to bed,and this morning, things are working almost normally. The only thing is that the Apache message comes up when I open a new browser window. I've checked to see that there's no local webpage sharing or anything like that. No new firewalls, nothing. Can anyone help?