If you install Office Web App for Lync and find that when users try to share a PowerPoint presentation and it is stuck on “Loading” then make sure that the latest WAC service pack (SP1) is installed.

After lots of troubleshooting, this solved our problem.

Steps on WAC Server

1. Launch powershell

2. Remove-OfficeWebAppsMachine

3. Apply WAC SP1 http://support.microsoft.com/kb/2880558

4. Reboot

5. Launch powershell

6. New-OfficeWebAppsFarm -InternalURL “https://wacserver.contoso.com” -ExternalURL ” https://wacserver.contoso.com ” -CertificateName “Certificate Friendly Name” –EditingEnabled

7. For the change to take effect immediately, restart the Lync