After running into several problems, I have removed CCSv5 and downloaded the latest release.
When I execute ccs_setup_5.2.1.00018.exe I get several anonymous failures ('Installation failed', I think - the log disappears after installing) with no indication as to what as failed, but the installation runs on to completion.
When I start the nerly-loaded CCS, it looks like it is starting a generic Eclipse release with no indication that CCS is involved.
Help/About gives a typical Eclipse popup, again with no sign of CCS.
What is going on!