Customer is trying to launch Symantec Installation Manager (SIM) and the following popup window appears:

"a fatal exception error has occurred"

Looking at the SIM logs, the following entry is noticed:

Uncaught Exception in Application Invalid URI: Invalid port specified.
 

SIM logs:

source="Symantec.Installation.SimApplication.CurrentDomain_UnhandledException"
module="SymantecInstallationManager.exe"
process="SymantecInstallationManager"
Description= "Uncaught Exception in Application Invalid URI: Invalid port specified."[System.UriFormatException @ System]
at System.Uri.CreateThis(String uri, Boolean dontEscape, UriKind uriKind)
at Symantec.Installation.FileDown

loader.InitializeUserProxyInfo(HttpWebRequest& httpWebRequest)
at Symantec.Installation.FileDownloader.DownloadFile(Uri sourceUri, Uri destinationUri, Int64 fileSize)
at Symantec.Installation.FileDownloader.DownloadFiles()
at Symantec.Installation.Managers.ProductListingManager.DownloadPlFile(String source, String destination)
at Symantec.Installation.Managers.ProductListingManager.GetLatestPlFile(String source)
at Symantec.Installation.Managers.ProductListingManager.GetAndLoadProductListings(String source)
at Symantec.Installation.Managers.ProductListingManager.LoadCurrentProductListings()
at Symantec.Installation.Managers.ProductListingManager.LoadAndUpdateProductListings()
at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()

Possible bad port reference added under the proxy settings.

In this particular instance, by cleaning up [HKEY_LOCAL_MACHINE\SOFTWARE\Altiris\AIM\Configuration\Users\AppIDaccount@domain\Proxy] and reinstalling SIM we were able to pass the error (after we were prompted to entry the proxy settings).
We selected automatically detect and we added just the user and password. It was not needed to add a proxy server nor a port entry.