Cannot login into MS Directory Synchronization Tool

Hello,

I have just fetched Microsoft Directory Synchronization Tool 9.1 from http://www.microsoft.com/en-us/download/details.aspx?id=22042, and installed it.
When I try to log in, I get 'Authentication failed', and Event Log reports:
- System
  - Provider
   [ Name]  Directory Synchronization Tool
  - EventID 1303
   [ Qualifiers]  0
   Level 2
   Task 0
   Keywords 0x80000000000000
  - TimeCreated
   [ SystemTime]  2/28/2014T08:38:55.000000000Z
   EventRecordID 25998
   Channel Application
   Computer STU-ADSYNC.exicom.local
   Security
- EventData
   The username/password combination is not valid Extended Properties: Exception: System.ServiceModel.FaultException: Authentication failed Timestamp: 2/28/2014 8:38 AM:55 (UTC) Process Name: C:\Program Files\Microsoft Directory Synchronization Tool\Microsoft.Ehs.DirSync.Dst.exe Category: General Priority: 5 Machine: STU-ADSYNC Application Domain: Microsoft.Ehs.DirSync.Dst.exe Process Id: 1224 Win32 Thread Id: 2376 Thread Name: 
C:\Program Files\Windows Azure Active Directory Sync\DirSyncConfigShell.psc1 works as expected.

Regards,

Marek