I was having a similar issue with Terran Tribune Joomla 1.5.9 (just upgraded from 1.5. .
Original installed using RocketLauncher, currently in the process of conversion to the client's own material.
When creating new articles or copying old ones the Read More link goes to a page with the message "To access the private area of this site, please log in."
I disabled search engine friendly URLs and was then able to track the issue back to an ItemID error.
When I changed the 45 to 44 and pasted it into the address bar the page appeared.
Another article showing the same error on that sector page was fine when accessed from the Category page where it had the itemid 43
I routed it back to the menu where permissions for menu item 45 (Markets in Rocket Launcher) were set to registered. The category Markets had been renamed and the articles were in that renamed category.
Also on the main menu was Sectors, which was also set to Registered and had a menu ID of 46. Items in the categories with menu IDs of 43 and 44 behaved as expected because they were set to Public.
Setting Sectors and Markets in the main menu from Registered to Public made the categories appear in the submenu and resolved the issue of clicking on Read More leading to the page with the message "To access the private area of this site, please log in.".
In addition it resolved the strange anomaly of an empty box sitting above the main article on that section page.
I hope that helps anyone else using Rocket Launcher who edits the existing sectors and categories and gets the read more link telling people they need to be registered to read the full text. Or indeed has items in the categories submenu on the section page which are not showing.