Congratulations on being another step closer to a full release.
I tried the RC and when trying to install a CB Plugin, I get this error:
"Direct Access to this location is not allowed."
I checked plugin/user and the files are there, along with a zipped file that should have been unzipped upon installation by calling the install.pluginname.php file (which uses PclZip).
Did you install the CAPTCHA plugin? I was running strong until i did, now I am getting the same thing...when I try to logout, check my profile, everything.
I did see that we are to set the permissions to 755, but I am on a Windows local install with full permissions, so not sure why I wouldn't have access.
[update] I unpublished the CAPTCHA and the issue went away for me.
I install the plugin straight after I install CB-RC, on a fresh 1.5.3 Joomla install.
I only installed the CAPTCHA plugin after I got the error message, just to test.
CAPTCHA installed successfully with a message about chmod().
Not sure if this is an issue, but this is what I see in php error log for CAPTCHA:
[01-Jun-2008 11:54:42] PHP Warning: chmod() [<a href='function.chmod'>function.chmod</a>]: No such file or directory in /Users/motd/Sites/joomla15/cb12test1/components/com_comprofiler/plugin/user/plug_cbcaptcha/install.cbcaptcha.php on line 47
I had to unpublish the CAPTCHA and all was well; then I installed MyBlog to check the Avatar sharing and the like...same thing happend. The "MyBlog Tab" plugin will fire the same message and I can't do anything.
Could be that the plugin is not specifically written for CB 1.2 (new API) or most likely it is not Joomla native and you do not have the Joomla legacy plugin installed.
There will be a new CB Captcha plugin compatible with CB 1.2 (and thus cross CMS compatible just like CB 1.2) within the day (check your documentation subscriber download area for it).
============ IMO: NO CB ISSUES HERE ==============