I found a solution at this web site
http://www.synetx.com/tips/?p=16=1
The solution was to reset the Windows Vista Winsock Stack
To repair and reset the Windows Vista Winsock Stack:
1. Click on Start button.
2. Type Cmd in the Start Search text box.
3. Press Ctrl-Shift-Enter keyboard shortcut to run Command Prompt as Administrator. Allow elevation request.
4. Type netsh winsock reset in the Command Prompt shell, and then press the Enter key.
5. Restart the computer.
What netsh winsock reset command does is it resets Winsock Catalog to a clean state or default configuration. It removes all Winsock LSP (Layered Service Providers) previously installed, including the potential malfunctioned LSP that causes loss of network packets transmission failure. So all previously-installed LSPs must be reinstalled. This command does not affect Winsock Name Space Provider entries.