Weird problem when on the Net

My system has starting to slow down and sometimes stop when on the net. Seems to be when waiting for a reply to a request like opening a web site. When opening my email I have to wait for a minute because when the page opens and I start to type the screen go blank and the page will redisplay....any thing that I typed will be gone. System is running on an ethernet cable. More problems seems to be when I back page it will take some time before the page will display. Has at times just hang and will not go back.

Another weird problem is when I try to download Flash Player it will not let it download. Just hangs and does nothing.

These program are more on Chrome than on Firefox. Also when I send it my work timesheet Chrome will not display the reply from my company but Firefox will. AT&T has run several test on the DSL line and said all is OK. Eithernet card problem maybe? I am beginning to think maybe a complete system failure is coming.

BTW...Lap top runs fine on wireless.