can you tell us what happens when you try to connect your macs ethernet port to your router or modem?
Can you also tell us what type of internet service you have?
One last question, What make andd model is the USB to ethernet you purchased?
Can you tell me what model your Macbook is so I can give you a couple of options to look at, Or can you take the adapter out and let me know if there is a model number on a sticker?
In that case it is an mb442z/a and this is the unit if I am correct?
If I am then it was designed for the MacBook Air and people have had a very limited amount of luck using them with other Apple machines as the adapter has a special chip in it that looks for an Air so that it is designed not work with other machines.
This article will explain it a little more if you are interested http://reviews.ebay.com/Reason-MacBook-Air-Ethernet-Adapters-Don-apos-t-Work-On-Macs_W0QQugidZ10000000007214447
The person who wrote the article produces an aftermarket USB to ethernet that will work with your machine without any modification straight out of the box for $20.00 http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320441247463&ih=011&category=11175&ssPageName=mem_guide:1&rd=1
Let us know if you need more info or clarification.
I agree 100%
Over the years they have manufacturered different adapters, however they have been propriitary to the model series which is why I prefer a universal unit so I can have it for all machines.
I actually carry one of the universal adapters with me so when I go to Mac clients I know I can plug it in and it will just work.
Let me know if you need more info.