After the installation of RollUp 4 there were issues getting to OWA on one of the CAS servers. 404 errors were received. After reregistering ASP with IIS via:
We received an error to check the ASP log. In the log, it was trying to create aspnet_client. This did not exist on the CAS server that was not functioning. We changed the home directory to c:\inetpub\wwwroot, reregistered, and iireset. The folder was created successfully. After changing the redirect back to owa as per their configuration, the login form came up again.
Upon trying to log in to OWA, however, we were presented with a new problem. OWA would log in, but then boot the user right back to the FBA login page. To solve this issue, all it took was recreating the OWA virtual directory with the following commands:
Remove-OwaVirtualDirectory -identity "CASSERVER\owa (Default Web Site)"
New-OWAVirtualDirectory -OWAVersion "Exchange2007" -Name "CASSERVER\owa (Default Web Site)"
Reset IIS again (iisreset)..
Users are now able to log in to OWA on this CAS server. Now all that was left to do was reenable NLB for the front end cluster, change he authentication settings back, change back the default domain, and reset the internal/external OWA addresses.