Hi @sofia.grade,
Unfortunately some users seem to experience issues on certain Mac configurations. We have looked into the issue a couple times but at this time do not have a clear diagnosis of the issue or recommendation for fixing it.
Most configurations of Macs continue to work, and we have no reports of this issue on other operating systems, so if you have access to other machines, that may be a route.
Alternatively, some functionality is available in the browser-based Allen Brain Explorer beta, which can be found here: http://help.brain-map.org/display/brainexplorer/Allen+Brain+Explorer+(beta)%3A++User+Guide