The MQSC BizTalk adapter only allows a single server namein the "Connection Name" property.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
This issue is fixed in the following cumulative update for Host Integration Server:
Note After you apply this fix, the Connection Name property allows a comma delimitedlist of servers. For example: MQSRV1(1414),MQSRV2(1414).