I get constant sync errors on my iPhone4 now. Here's what happened:

1. Desktop and iPhone 4 were in perfect sync, all works well
2. I then enter a watched info for a disc I watched for the first time, using the iPhone 4 app
3. I sync the iPhone 4 with the desktop:
- sending works fine and when I check the desktop, the Watched data is nicely transmitted
- iPhone 4 reads the desktop collection just fine
- next step iPhone 4 want to download profiles from the desktop, I get this error:

There was an error synchronizing : *** - [NSPLaceholderMutableStringinitWithString:]: nil argument

Any idea what causes it? Every time I try to sync the iPhone 4 with the desktop, I get that error now 

No, both as far as users, profiles and anything else was concerned, DVDP desktop and DVDP app were perfectly the same. I had done a sync before adding the watched data so both were identical.

I then entered watched data for one user for one profile. The upload works fine but it's the download from desktop to iPhone that now gives that error.

The profile I entered watched data for was part of a box set. I don't know if that makes a difference or not ...

Oh wait, now I remember that for the user whom I set watched data for, I did an update on my iPhone of that particular user, using the import feature to grab contact details like e-mail address from the address book in my iPhone. The effect was that one e-mail address got changed. I see now that that change in e-mail address wasn't transfered to the desktop version. Could that be the cause?