Here's a great tip sent to me by Sebastian Gernert, one of our Support Escalation Engineers in Germany. Apparently this came up in a forum post so we can't take all the credit but I've written up the summary below:
Issue: When attempting to refresh the server from within the client software you may get the following error:
"The application Virtualization Client could not update publishing information from the server <serverName>.
The Application Virtualization Server has returned an Internal System error. Report the following error code to your System Administrator.
Error code: XXXXXX-XXXXXX0A-200001F4"
It's also possible that you can’t logon to the Server Management Console and receive “Error Code C803“.
Cause: This can occur if MSXML 6 is not installed prior to installing the App-V 4.5 server.
Resolution: Make sure that MSXML 6 is installed prior to installing the App-V server. You can download MSXML 6 here.
MSXML 6.0 is supported in Windows Vista; Windows 2000 Service Pack 4; Windows Server 2003; Windows Server 2003 Service Pack 1; Windows XP Service Pack 1; Windows XP Service Pack 2.
MSXML 6.0 is preinstalled with Windows Vista. For earlier versions of Windows, you can install MSXML 6.0 as a separate download.
MSXML 6.0 also comes with SQL Server 2005.
J.C. Hornbeck | Manageability Knowledge Engineer