Ok, i have created a directory with a smaller set of files. With this set of files s3sync performed flaweless.
I then just have deleted all the already uploaded files on S3, deleted the bucket, recreated the bucket, sync my original set of files and now it works as a charm.. I guess due to

? the file info of the orginal bucket was corrupted or what. Anyway, it works now perfectly.. and thanks for your help.
hnzz