After a quick look in the code of the server, I think I found what can causes this bug.
In the V7.0 because of the changes in res.partner and res.partner.address, the method name_search() has changed.
In the method in the V7.0, to get the ids to read, there is a sql request, so the request doesn't consider the companies and access rights.
If one of the ids is from the other company, then "Access Denied" is raised.
I'm maybe wrong but you can have a look in the file server/openerp/addons/base/res/res_partner.py
After a quick look in the code of the server, I think I found what can causes this bug.
In the V7.0 because of the changes in res.partner and res.partner. address, the method name_search() has changed.
In the method in the V7.0, to get the ids to read, there is a sql request, so the request doesn't consider the companies and access rights.
If one of the ids is from the other company, then "Access Denied" is raised.
I'm maybe wrong but you can have a look in the file server/ openerp/ addons/ base/res/ res_partner. py