Plesk 8.2.0 backup

Hallo an alle, seit dem ich das Plesk Backup über die Pleskoberfläche von lokaler Sicherung auf FTP umgestellt habe bekomme ich bei manchen Kunden-Backups folgende Fehlermeldung:

Following error is occured during scheduled backup process:

Error in UploadToRepositoryState.doActivityRunner()
Traceback (most recent call last):
File "/usr/local/psa/admin/share/agent_runner/agent_runner.py", line 98, in doActivityRunner
newState = self.doActivity()
File "/usr/local/psa/admin/share/agent_runner/agent_runner.py", line 427, in doActivity
remotefh = remoteBackupFile.fh('wb')
File "/usr/local/psa/admin/lib/python/backup.py", line 360, in fh
self.file = self.ftp.file(self.filename, mode)
File "/usr/local/psa/admin/lib/python/ftputil/ftputil.py", line 226, in file
host = self._copy()
File "/usr/local/psa/admin/lib/python/ftputil/ftputil.py", line 202, in _copy
return FTPHost(*self._args, self._kwargs)
File "/usr/local/psa/admin/lib/python/ftputil/ftputil.py", line 141, in __init__
self._session = self._make_session()
File "/usr/local/psa/admin/lib/python/ftputil/ftputil.py", line 196, in _make_session
return ftp_error._try_with_oserror(factory, *args, kwargs)
File "/usr/local/psa/admin/lib/python/ftputil/ftp_error.py", line 85, in _try_with_oserror
raise PermanentError(obj)
PermanentError: 530 Sorry, the maximum number of clients (3) for this user are already connected.
Debugging info: ftputil 2.1.1, Python 2.4.1 (linux2)

Plesk Version: psa v8.2.0_build82070807.17 os_SuSE 10.0
Server bei Strato mit 80GB FTP Backupspace

Kann mir jemand dazu etwas sagen an was es liegen könnte?