Birthday Reminders

Check iCal preferences.

Is "Show Birthdays calendar" ticked?

Sorry but it seems subscripted calendars can't show in iphone if your syncing is over the air, to see them you must sync using itunes, I have the same problem. Maybe Apple will fix that on next update release.

I have the same problem - when you say sync over iTunes, do you literally mean just plug in and sync, or do I need to sync my calendar manually on iTunes?

The birthdays calendar is a subscribed one in ical, and currently not able to be synced OTA with Mobile me, this will be correct in 3.0 this summer - this may help

http://www.appleinsider.com/articles/09/03/17/iphone3_0_adds_copy_paste_mms_forusers.html

As a workaround if you are using Mobile me as I do you could export your subscribed birthdays calendar from ical and then import it back into ical, as it will then appear as a regular calendar (you may need to rename it). This will then sync OTA via Mobile me. One point to note because this is not subscribed this new calendar will not update and any changes will have to be done manually, or the process above repeated.

Not perfect, but may be a short term solution for you until 3.0.

Yes, just plug in and sync in iTunes, before tick the "replace Calendars on that iphone". Don't sync over the air the calendars if not, subscripted calendars won't show up again.