Help Missing phone calendar

[Mercifull]

Since updating firmware to Froyo (Orange) I appear to have lost the built in phone calendar. My other calendars are showing Exchange, PC Sync and Facebook. If I click add calendars it also gives me the option to add my Gmail calendar too but the phone one is missing.

This is also the case on my girlfriends phone also on orange. Doe anyone have a solution to this?

Cheers