Uh... that's some painful number.
Did the application actually hang (i.e. did it never finish), or was it just unresponsive for 10 seconds, or a minute or two? The latter could be quite "normal" because as long as files are being added, the GUI gets little (no) opportunity to react to events.
Don't know if that will help, but maybe you want to disable the class-browser before doing that kind of mega-heavy stuff.
In that case, the classbrowser does not read and parse each and every file in addition to the work the project manager has to cope with, so you save some CPU power.