Have you found a solution to this yet.
I can update plug-ins that are already installed, but as far as using the Plugin Browser/Installer or the 'install' links on the new plug-ins I get the 'You do not have sufficient permissions to access this page.' message.
I've already tried the permissions to 777 and opened EVERYTHING up all the way (I know, dangerous) just to see if it would work, but it didn't and then closed everything back down to the more secure 644 and 755. So file permissions Obviously don't seems to be the problem.
I've manually deleted all the files on the host and uploaded a fresh install, and still no go.
I've even used the database cleanup script somebody suggested in another thread and that didn't help either.
Has anybody found a solution to this yet? There are a lot of threads on this topic, but I still haven't found one with a solution.