We’ve had a handful of reports about this now and it is indeed most odd.
The answer seems to be to simply install the full setup file (rather than the update) over the top of your existing installation. This will not affect your data in any way, but it will make sure that all the ClinicOffice program files are updated to the latest versions
Here’s a direct link to the full setup file :-
http://pioneersoftware.co.uk/files/cov5/cov5_setup.exe
In all cases (so far) this has resolved the issue – please let us know if you need any additional assistance.