If you have selected with a check all the calendars that you would like to see displayed but then when you click into another area you then have to re-select all the calendars again (see screenshot below which shoes all the calendars have been selected) then this sounds like a caching issue on your browser.
Please try clearing both the cache and cookies on your browser and see if this then resolve the issue for you.
To see how to clear cache and cookies in Google Chrome please click here.
To see how to clear cache and cookies in Firefox please click here
To see how to clear cache and cookies in Safari please click here.
Please try removing the check from the top 'My Calendars' checkbox and the 'Other Calendars' checkbox and JUST make sure that the checkboxes selected are for the named calendars only (as shown in the attached screenshot) - this may then resolve the issue.
If this does not resolve the issue please contact our Support Helpdesk for assistance.