Sorry for the late reply.
Unfortunately I have no idea what causes this message.
To debug this properly would require installing different versions of Java on my system and trying to reproduce the issue, which would probably take more time than we can spare at the moment.
In fact Java support for Max For Live has unofficially been given up on by Cycling '74 in as much as they have not addressed several known issues with it for at least 5 years, so I’m thinking I should probably remove Bonjour support for the LiveGrabber plugins entirely (or build cross-platform Bonjour C++ externals, but this again is out of scope for the moment).
I guess am reluctant to remove this feature since I spent quite some time making it work and considered it an essential feature of an OSC system since it is the only way that using two computers connected with OSC will immediately work on any network.
I will add this as a todo on my list, thanks for pinging me about it. In the mean time, you should be able to continue to use the LiveGrabber plugins without Bonjour by entering an exact IP address.