After installing BlackPearl when I clicked any of the 'Feature' links from the K2 Administration tab in Central Admin, I was getting the following error;
"The site http://<server>:<port>/ could not be found in the Web application SPWebApplication Name=SharePoint - <port> Parent=SPWebService."
I noticed that the reported site was my SSP Administration web application. Because I had this on a different port to MOSS, the only Site Collection is ssp/admin and there is no 'root' site collection. I tried deleting the SSP and web application, and the feature links then started working. I created a new SSP on a different port and it stopped working again. Then I tried adding a blank site collection at the root of the SSP Admin web application and they started working again.
I assume this means that there is an error when the BlackPearl link enumerates the site collections in all of the web applications and it expects there to be a site collection at the root of the web app.
So a work around is to create a blank site collection in the root of your SSP web application. (Or put your SSP in the same web application as your other sites)