I just submitted by details, but went back to check the calendar again, and it's now working. I have no idea why all of a sudden it has started working again, as I haven't upgraded or changed anything on the site since it stopped working. But, anyway, you can ignore my login info submission. Hopefully, the problem won't reappear.
I had the same problem. It began with update to 1.0. Calendar showed this message “here was an error while fetching events!”. After checking my tasks and entering a user for every task the error was gone.