A problem has been encountered while loading the setup components. Canceling setup.
After installing Visual Studio 2008 and Service Pack 1 from my external HDD I tried modifying the installed features by re-running the original setup. During the initialisation of the setup I received the error “A problem has been encountered while loading the setup components. Canceling setup.” and the setup then terminated.
The workaround was to run the setup from Add/Remove Programs (or Programs and Features in Windows Vista/7) instead of running it from the original installation source. I suspect that this is because the RTM installer doesn’t recognise the service packed components.