Well basically I used to own a site with PR 3 or something similar. I then sold this site to someone and when I checked back to this site not long ago it had PR zero? The only links it had be4 were dir lnks.
There are quite a few possible situations here... - Directories dropping links like you mentioned - Directories going down in value/losing PR themselves - PR fluctuation. Especially now with another update coming - Errors... Have you checked http or www version? Have you checks all the DCs? - Domain getting banned and more...
Thanks for answers guys. And what he means by illegal link building is link spam. That is using automated software to drop links everywhere.