fyi, I tested this today with the latest Mono built from svn and the bug does exist in the ContentManager.aspx page. It seems to be a general GridView problem in Mono as the oproblem also happens in Admin > Core Data > Tax Class Administration, and other pages where we are using in place editing inside a GridView.
I filed a bug report https://bugzilla.novell.com/show_bug.cgi?id=517172
actually I filed 2 other bug reports as well
https://bugzilla.novell.com/show_bug.cgi?id=517170
https://bugzilla.novell.com/show_bug.cgi?id=517168
Best,
Joe