We haven't seen this issue at all. We are running several 10.7.3 machines on campus and haven't had an issue so far. I've also tested it with 10.8 and haven't seen anything yet but I will continue to hold my breath on that one.
That error only occurs when the Popup.app is unreachable by the CUPS backend (usually because it's not running). If you do not have the most recent version of the Mac Popup client, you should download it from the sidebar links on http://pharos.custhelp.com (or http://www.pharos.com/support).
Older versions of the client tried to register Popup.app as a login item, but OS changes in 10.7 disrupted that, and the newer clients should start Popup.app as a LaunchAgent.
It's also possible you have the new client, but it is crashing/aborting for some reason... in that case, you might need to enable popup logging as per this kbase article: http://pharos.custhelp.com/app/answers/detail/a_id/1059.