ORKUT Here is way to add related community when it fails to show up in search results:

1. Go to your community and click 'Add' button in your related communities section.
2. Search for any community (it can be any, not the community you want to add).
3. When you see results, paste the below text in address bar and press Enter key.

javascript: document.forms[2].relatedId.type='text';void(0);

4. You will see a input text box for entering the community ID in the first search result. Now just enter the ID of community you want to add as related community, and click on "add" button.