I am trying with Multi company. I have created companies 'company A' and 'Company B' both as parent companies and created two users for each companies. But the users are not able to create the product or customers. It is showing a message as

Access Denied

The requested operation cannot be completed due to security restrictions. Please contact your system administrator.

(Document type: Partner, Operation: read)

If i set parent company for 'Company A' and 'Company B' as 'Your Company' then its working with out any issues