IN reply to this

http://www.geekzone.co.nz/forums.asp?ForumId=39&TopicId=16914&page_no=1#100255
 
Chocobo1 was still experiencing issues... This maybe to late but anyway.. Mine actually started doing what yours is doing where the ADSL light turns off and then you need to cold-reset it to get it going again.

Go to here: http://www.dlink.co.nz/tech/

Select your model and follow the steps to update your Firmware. This resolved all issues for me.
I haven't had a wireless or Wired link drop yet.