Hello, today I received this mail from Sony Ericsson support:
Dear Customer,
Thank you for contacting Sony Ericsson Call Center.
When an email account is set up on the Sony Ericsson P1i not all types of calendar items will be synchronized to the Mac computer. The calendar item types Appointment and All Day Event will not be synchronized to the Mac computer when having an email account set up on the phone. Reminders and Anniversaries are not affected by this problem.
The solution for Mac OS 10.4.x is to delete the email account set up on the phone. According to the latest information this will be fixed in Apple Mac OS 10.5 Leopard.
Best regards,
Sony Ericsson Call Center