For the past week or two I have been asked to re-enter license key details for several programs. could CCleaner be responsible for deleting the key information?
It shouldn’t be and I have never know it do anything like that before.
You don’t mean that it is logging you out of websites in your browser and that you need to enter your pasword do you?
If it is actual programmes that are asking for their registration keys then:
Are you using the software updater? (Some softwares may ask for their keys again after an update).
Are you using the Registry Cleaner? (Which may be removing saved keys).