Guillaume, a friend who works in Montreal, wrote to me to share an issue they encountered recently.
We noticed a weird issue with one of our Revit projects. The expected (normal) time to open this model was about two and half minutes. On some machines it would take as long as eleven minutes and browsing through the project was rather slow. We also noticed that there was a pronounced lag while working in the model, while zooming and panning on sheets for example.If you are going to start using Revit 2014 by upgrading a project you'll want to be aware of it. If you have had a similar experience then check to see if iTunes is installed. You may need to remove it completely. If you don't allow the installation of iTunes on office computers it shouldn't be an issue. If users can install software then you'll want to check. It's not safe to assume simply having a rule against installing software is enough.
After systematically isolating every possible cause that we could think of, we found and we have no doubt, that the iTunes suite of software (including “Bonjour” process) is the culprit. We suspect the likely cause of this is that “Bonjour” uses the same port and background process as some parts of Revit, for example Worksharing Monitor.
We tried removing iTunes from the computers that took nine minutes to open the model and it always solved the issue. We also did the opposite. We installed iTunes on machines that opened the project normally and then they took about nine minutes to open. It is the first time I've seen this presented to us so obviously. We are using Revit 2014 primarily. We don't know if this is true for older versions of Revit.