I had a similar problem back in 2010 and again yesterday.
The solution provided by Arturia (after they initially tried to blame a defective USB dongle, USB hub, or computer) involved uninstalling ELCC, running three Terminal commands (which they said could possibly do serious damage to the computer if entered incorrectly), reinstalling ELCC, and running another Terminal command.
This time, ELCC was throwing errors when scanning V-Collection 3 after I installed the new version of Digital Performer (8.0). (I'd previously been running DP 7.24.)
After the errors, ELCC would stop seeing the USB dongle, even though the Mac saw it, and the LED was lit.
The V-Collection was already installed and fully up to date, as was ELCC, and Mac OS 10.8.2 on my Mac Pro. Some of the V-Collection plugins DID pass inspection, but when there were about 7 remaining, the problems started.
The two errors I got were:
1. 'Application 'Synsopos.app' could not be started. Probably the file is corrupted or incompatible, or file access permissions are set incorrectly.
Please download and install the latest version of the eLicenser Control Software from....'
I'd click OK to abort, and then DP would try to verify another Arturia plugin.
After a while, I'd get:
2. 'Application 'Unknown Application' has caused the following error:
An unknown interapplication communication error occurred. In case the problem persists, please close all applications and restart your computer.'
At this point, if I launched ELCC, it would no longer see the USB dongle.
I tried the lengthy procedure from 2010, and it worked - kind of.
I had to restart the computer (which was not in the initial procedure from Arturia). After this, DP then successfully scanned the six V-Collection plugins which had been previously skipped, but CS80V2 still gave an error. And again, I launched ELCC and it did not see the dongle.
I restarted the computer again, and then launched DP8. This time, CS80V2 did pass the inspection.
In my experience, the Steinberg e-Licenser has been a real pain. It's very buggy, and as a result I've lost many hours troubleshooting. I wish Arturia would switch to another copy protection system, like Spectrasonics, Nomad Factory, Overloud, Toontrack, and others, who allow two disk authorizations (e.g., laptop and desktop) and avoid the USB dongle completely.
It's absurd to have to enter commands in Terminal just to use a piece of consumer software.