I think I understand what you are doing now as you say on my demo site that:
Feature Installation/configuration is not available
Configuration settings made there only set default values that will be used when a new instance of a feature is added to a page, it will not affect instances already on a page. If you visit the page that has your event calendar pro on it then click the gear icon next to the title of the calendar you will see the instance specific settings and there you should be able to specify the time zone.
Now that I understand what you were trying to do I am able to produce the error you mentioned and will look into fixing that asap so its fixed in the next release. It looks like a mojoportal bug rather than a bug in Event Calendar Pro. Admittedly I rarely use those feature configuration pages, as those settings also come from config files, so I typically have just made changes to the config file and then visit /Setup/Default.aspx also updates the default settings in the db based on the config file. In fact if you were to change a default setting in that page without changing the corresponding feature config file, then visiting the setup page will restore the setting from the config file. The web page for managing those settings were there before we had the installation system but I kept it because it makes it easier fopr developers to configure their custom features without having to learn about the setup system. So its mainly used for features that don't have config files, but all the mojoPortal features do have the config files.
Hope that makes sense.
ps Was not able to login to your site, but if you continue to have problems let me know and I'll contact you by emaill for login info.