I think I must deinstall Omnifocus on both iMac and iPhone/iPad as sync is a nightmare. Every first sync works in the Wifi environment and then it constantly failes. Also the following links cannot be acessed quite often neither via LAN acess nor via Wifi.
forum:
http://forums.omnigroup.com/forumdisplay.php?f=63
Sync Setup:
https://manage.sync.omnigroup.com/