I suppose I could just renew the Ethernet card....do these things become faulty with the symptoms I have...pages going slow after being online for a while
A definite YES to that question. Ethernet cards are usually dirt cheap and simple enough to replace.
Have you tried checking to see if your operating system has recorded a fault? Go -> Control Panel -> Device Manager -> Network Adaptors ... then select your card and double click on it.
Under the menu heading "General", there will be a box in the lower part of the window that is headed "Device Status".
This box will advise you whether Windoze reckons the device is working properly, or has identified a fault.