Hi there,
When restarting myCal PRO on your iPad, are you given the option of emailing a crash log? If so please send it through and I will take a look.
Can you also go into the standard iPad calendar app and edit the same event. Is there an Invitees button, can you send me a screenshot? It sounds like myCal PRO isn't correctly detecting the Invitee field in iOS 5, but it certainly shouldn't cause it to crash so I will need to investigate both.
To take a screenshot press the Power and Home buttons briefly at the same time. The screenshot will be added to your Photos app, please email it to
support@johnhair.com.
Thanks!
John