Merge Replication Primary Key Violations

I have a Merge Replication Problem and I'm not sure how to proceed.
Given the following:
Multiple clients have merge subscriptions to a central Server's DB.
DB contains a table tblUser
tblUser has a Varchar field; UserLoginName, which is Primary Key.
It also has an integer field, UserValue

The replication is configured to resolve to the greater integer value.

Client 1 creates a new User
INSERT tblUser
(UserLoginName, UserValue)
VALUES('Fred',1)

At the same time Client 2 does the same thing, but with a larger value
INSERT tblUSer
(UserLoginName, UserValue)
VALUES('Fred', 2)

One of the inserts will get to the Central Server first.
The other will form a conflict.
A row insert at 'Client2.dbUsers' could not be propagated to 'CentralServer.dbUsers'.
This failure can be caused by a constraint violation.
Violation of PRIMARY KEY constraint 'PK_tblUser_1'. Cannot insert duplicate key in object 'dbo.tblUser'.

So now I have two different value fields and a conflict that cannot be resolved.

Is this fixable?
Do I need to make changes at athe Architechture level?