I have been having a recurring problem with one user, they have an iPhone 3gs, that is updated to current OS. Contacts, calendar and email works ok for a while, but then the calendar will disappear along with the contacts. I then have to delete the account off the phone and out of mobility to get things working again. Sometimes the contacts will then only sync to a certain point, could this be an indicator of the invalid folder ID ? Email seems to work ok.

Also, looking at the logs, the user is continually authenticating and then throwing the invalid folder id message.

What does the invalid folder ID relate to ? Calendar or contacts ?