I have that exact same error here – please help!
The activity failed: Attempt to write to file /homepages/11/d355786251/htdocs/13test/wp-content/plugins/wponlinebackup/tmp/backup.zip.enc.b0339e3a1a317eac2371af1d73e159b7015bd067.rc.php only partially succeeded. Only 0 of 0 bytes were written. (11918992 bytes already written.) PHP last error: No error message was logged.
Online Backup for WordPress Plugin Version 3.0.4
WordPress Version: 3.8.2 (standalone)
PHP Version: 5.4.27
Server Software: Apache
MySQL Server Version: 5.1.73-log
MySQL Client Version: 1.0; MySQL Packet Size: 10 MiB
Memory: 256M; Post: 8M; Upload: 40M; Timeout: 50000
Memory Changable: Yes; Admin Cache Size: 71.59 KiB
Status: 1 row, 25.31 KiB packet size, 62.38 KiB cache freed, 11.16 MiB memory used
Capabilities: hashcopy gzdeflate php5hash DES AES128 AES192 AES256
End of Information
