Again, thank you very much! Raising the Silverlight Isolated Storage Quota let me sync all of my data successfully.
Just for the records, this is the helper method i added to the example client:
private void EnsureStorageSpace(long expectedSize)
{
using (IsolatedStorageFile storage = IsolatedStorageFile.GetUserStoreForApplication())
{
if (storage.AvailableFreeSpace - expectedSize < 0)
{
storage.IncreaseQuotaTo(storage.Quota - storage.AvailableFreeSpace + expectedSize);
}
}
}