I use Directnic as I have sites registered through them but I find a lot of the time that their system can't access the whois info.
In the UK I use easyspace.co.uk, tucows.com and now goddaddy.com but they all seem to be employing the password access system. I think this is stop stop spiders accessing the whois info for bulk domain buyers to back order a site due to expire..
NetSol often shows just basic info as the site is registered through a company who use the password system, so just go to that site and use the password they give..