I had a couple of sites with PRs of 3. Then, one fine day, the PRs all dropped to 0. Can I find out if anyone knows the reasons that can contribute to this happening? Also, would one of the reasons be that my article is not indexed yet before I submit to article directories and google is penalising my site for it?
First, check if your site is banned. Key in site:domainname.com and do you find your site listed? If no, then it has been banned and removed. You will have to rectify your site according to the Google Webmaster Guidelines. After that, send them a reinclusion request. If your site is indexed, then most probably you have lost most of your inbound links pointing to your site. Did you change anything related to your domain name recently? Did you buy any high PR links way back that happens to expire already?
It might prove usefule to check against various DCs to see if it's just a sync or flucuation - the toolbarqueries may in fact be a 3 but the DC you're tapping at the moment might only be a 0. Otherwise, it's a matter of losing BLs most likely ...