Please need help with how to resolve this error:

Insert failed. First exception on row 0; first error: UNKNOWN_EXCEPTION, java.lang.IllegalStateException Programmer Error: you cannot mix EntityObjects with different UddInfos within one transaction: id = null: [] stack Class.MM_AccountSharingTest.testAccountSharingTrigger: line 74, column 1

Here is my code snippet (line 74 in red):

static testMethod void testAccountSharingTrigger() {

Id adminProfile = [Select Id From Profile Where Name = 'System Administrator' Limit 1].id;

Id dmeProfile = [Select Id From Profile Where Name = 'DME Portal User' Limit 1].id;

 // Select admin user. 

 Id roleId = [SELECT Id FROM UserRole where Name = 'System Administrator' ].id;

Id adminUser = [SELECT Id FROM User WHERE IsActive = true and UserRoleId = :roleId LIMIT 1].id;

  Id type1Id = [Select id from RecordType where  SobjectType = 'Account' and Name = 'Implanting Center'].id;

  Id type2Id = [Select id from RecordType where  SobjectType = 'Account' and Name = 'DME Center'].id;

      //create a new Sys Admin user

     User sysAdmin = new User();

      sysAdmin.Username = 'sys.admin_testAccountSharingTrigger@test.com';

      sysAdmin.Email = 'admin.ser@test.com';

      sysAdmin.Alias = 'admin';

      sysAdmin.CommunityNickname = 'admin';

      sysAdmin.TimeZoneSidKey = 'America/Los_Angeles';

      sysAdmin.LocaleSidKey = 'en_US';

     sysAdmin.EmailEncodingKey = 'UTF-8';

     sysAdmin.ProfileId = adminProfile;

      sysAdmin.LanguageLocaleKey = 'en_US';

      sysAdmin.FirstName = 'Sys';

      sysAdmin.LastName = 'Admin';

      insert sysAdmin;  -------  this is line 74

    // Create new account. 

      Account implantCtr = new Account();

      implantCtr.Name = 'Implanting Center Account';

      implantCtr.BillingCity = 'San Diego';

      implantCtr.BillingPostalCode = '92121';

     implantCtr.RecordTypeId = type1Id;

     implantCtr.OwnerId = adminUser;

      insert implantCtr;

}

Thanks,

-ST