Mysterious appearance of new untitled calendars

In the past week I've had three new, empty calendars appear in the calendars menu of iCal. The pattern seems to be a new one appears the for 3 days or so it appears and disappears like a Christmas tree light then remains present after that. I've tried to delete these rogue calendars but the always come back. If the just sat there and were just clutter, I would bother with them. But when the flashing one does appear, anything you enter in that few moments is recorded on that calendar but then disappears after a few cycles of the flashing. I'm wondering if it's a sync'ing problem but have no evidence of such blame.

Hope someone has a clue on this!