I've got the file, however, I found some info that might affect this:
http://www.bleepingcomputer.com/forums/topic312743.html
This and other articles lead me to believe that simply overwriting ndis.sys could lead to further system instability. Other actions need to be taken; they are registry related. In addition, a corrupted system file may not be your biggest concern right now, as similar issues tend to point towards a virus infection, and in WCS, a rootkit. If you can hop on a 2nd computer with MSN or Skype, we can keep working on this. I need more details.