Mac users, just like Windows users, have issues with Java sometimes. Here’s a screencast that explains how you can begin the troubleshooting process before calling the friendly support person.
For users of Blackboard the most common problems seem to revolve around Java, so if you first clear your cache, delete the security certificate, restart your browser, and log back into Blackboard, that might solve your issue. If it doesn’t, then your efforts will give you a head start in the troubleshooting process.
Photo by cesarastudillo and republished here under a Creative Commons license.