Invalid SSL certificate : Certificate is for web.mysite.com, not 178.xxx.xxx.xxx (again?)

I opened this topic but it seems to have disappeared so here it is again:

When I click on the "Open Webmin" button in Cloudmin of my monitoring server for any of the managed systems, I get an error:

Invalid SSL certificate : Certificate is for web.mysite.com, not 178.xxx.xxx.xxx

I just noticed this recently, previously all was working just fine. Anybody has an idea on why this happens?

I moved the topic to Cloudmin section, so this one can be deleted.