Vulcan wrote:

I have a recurring event into which I've inserted some conferencing
telephone dial up numbers.

If I edit a single occurrence of the event, and delete the conference
numbers, then save the event, the default text (the above conferencing
numbers) are gone from the event.

Then I re-edit the event, past in some new text and save the event -
pretty normal so far. When I reopen the event to edit a third time
(or just look at the event in the preview pane), the conference
numbers that I deleted in edit #1 are back, and the text I just
pasted is nowhere to be found!

Depending on how you modify a recurring event, the item may be being
regenerated, which eliminates exceptions.
--
Brian Tillman