Two Computers with the Same Username and Computer Name in Homegroup

User A on Computer A has created a homegroup on Ultimate.
User B on Computer B has joined the homegroup with Home Premium.
User A on Computer A(on another Ultimate) has joined the homegroup.
(All 64 bit)
(Shortly, there are two computers with the same username and same computer name such as John on John-PC.)
(They are never connected at the same time. - They can not anyway. They are on the same computer, but in different partitions.)

Second User A does not have access to the shared libraries or folders (which are shared as homegroup read/write). Why?
Can the problem be solved?

UPDATE: It is working now, I couldn't find an option to delete the post.

I would really rename one of those machines.