I think I found the fix;

This error will occur if you have been given delegate rights to someone's
Calendar but not given rights to their Tasks and are trying to print their
calendar using the Daily Style which includes printing task items. The
delegate can resolve this problem by modifying the Print style to exclude
task items. This can be done by selecting File | Print and clicking on the
Define Styles button. Highlight Daily Style and click on the Edit button.
Then uncheck the Include TaskPad option and click OK. You will now be able
to print the calendar.

Alternatively, the calendar owner can modify delegate rights to include
permissions for Tasks.