If the ballasts aren't too difficult to get to, you should be able to reverse the left and right ones. If the problem follows the ballast, you found the problem. Otherwise it's the bulb or wiring to the ballast...
There is a pirate site with the FSM (Factory Service Manual) available. I can't believe it hasn't been shut down yet!
http://www.phatg20.net/modules...id=62
You'll have to find the software to decompress .rar files, but that's available free as well (google search).
The legitimate downloads are available from
http://www.infiniti-techinfo.com with a one day $20 subscription. You can also download the TSBs (Technical Service Bulletins) there which are plentiful for the 2002 Q45. I assume you are out of warranty coverage?
Heath