Inspiron 1521

I have a dell inspiron 1521 and ive always used an ethernet connection but all of a sudden my laptop isnt picking up the connection (wireless still works fine).  Ive reinstalled Vista several times so im not sure if that has anything to do with it.  Does this sound like a hardware issue or a software issue?  In the past, ive reinstalled vista and for whatever reason when I logged back into windows my scrolling bar didnt work so i had to reinstall some software from my drivers and utilities disk.  Let me know if you have any thoughts on what could be the problem, im thinking i might have to get some hardware replaced.