Okay, here's the setup using WP 2.7.1 and Role Scoper 1.0.0 and Ozh Admin Drop Down Menu plugin 3.1.3.3.7:

Add a new page called MyPage with a few lines of content.

Add a new category called MyCat, and then add a new post to it.

Setup a new user called MyUser, and give it only Subscriber privileges. Do NOT add it to any other groups or roles yet.

Under Users-> Groups setup a new Group called MyPage Users Group, and assign MyUser to this group.

Now setup another new group called MyCat Users Group, and assign MyUser to this group as well.

Go to Roles-> Pages and choose Assign For Selected And Sub-Pages, then check the MyPage Users Group and then check the Page Editor for MyPage.

Now go to Roles-> Categories and choose Assign For Selected And Sub-Categories, then check the MyCat Users Group and then check Page Editor for MyCat.

So you should now have a user called MyUser with WP Subscriber privileges, and assigned to the MyPage Users Group and the MyCat Users Group. The MyPage Users Group should have Page Editor privileges on a page called MyPage, and the MyCat Users Group should have PAge Editor privileges in a category called MyCat.

If you login as this user, they should be able to access and edit any MyCat posts. You might or not be able to access and the MyPage though. But now, if you remove MyUser from the MyCat Users Group, so they are only in the MyPage Users Group, and log back in as this user, from the Dashboard you will definitely not be able to access MyPage. Instead you get a 404 error.

If I disable Ozh Admin Drop Down Meny plugin, the problem seems to go away.

I will also post this on Ozh site.

Thanks

Tested in WP2.7.1 with Ozh Admin Drop Down Menu 3.1.3.3.7 and it appears to work now.

Thanks