Please note that there was a recent update to Blackboard (November 5, 2013) and you may be receiving this error.

This error is caused by files on your system not matcing the files that Blackboard is expecting to see. If you are receiving this error, your options are to use a different Internet browser, or to clear your java cache.
Source: http://www.java.com/en/download/help/plugin_cache.xml
How to Clear Your Java Cache on a Mac
- Click on the apple in the top left corner and select "system preferences"

2. Click on "Java" (under the "other" section)

3. It should automatically open to the "General" tab. In the area labelled "Temporary Internet Files" select "Settings..."

4. Click the "Delete files..." button, then exit the Java/preferences. You may need to restart Safari.

How to Clear Your Java Cache on a Windows PC
- Click on the Start button and then click on the Control Panel.
- Find the Java Control Panel.
- Click on the Java icon in order to open the Java Control Panel.

- It should automatically open in the General tab. Click Settings under the Temporary Internet Files Section.
- The Temporary Files Settings dialog box will appear.

- Click Delete Files. The Delete Files and Applications dialog box will appear.
- Click OK. This will delete all of the downloaded applications and applets from the cache.