Hi Valdy,

As a quick solution, I suggest that you can bypass Lync 2010 Autodiscover and DNS resolution.

The Lync 2010 client can be set to use manual configuration to determine whether the sign-in issue is related to DNS resolution issues. If manual configuration works and automatic configuration does not work, it usually indicates a problem with DNS resolution. This usually occurs because the DNS SRV records are not present or are inaccessible from the client computer. To set Lync 2010 to use manual configuration, follow these steps:
1. In the upper-right area of Lync 2010, click the Gear icon to open the Options page.
2. In the Lync - Options dialog box, click Personal.
3. Next to the sign-in address, click Advanced.
4. Make sure that Manual Configuration is selected and that the configuration values are exactly as follows:
   Internal server name or IP address: sipdir.online.lync.com:443
   External server name or IP address: sipdir.online.lync.com:443
Important If manual configuration works but automatic configuration still fails, the issue is not resolved. Follow the steps in the following article in the Microsoft Knowledge Base to confirm that the correct Autodiscover records exist:
http://support.microsoft.com/kb/2566790

For more information of Lync Online troubleshooting please refer to the article below:
http://support.microsoft.com/kb/2541980

Thanks,
Alex Du