The issue with Blackboard not allowing uploads from Safari has been fixed. The issue stems from a change that Apple implemented which caused Blackboard to change the code it used to upload files from local machines. HOWEVER, if you tried to upload documents during the period between when Safari was updated and when the fix was applied, Safari will have placed some code in its cache that will need to be removed before you can get back to uploading documents using Safari.
Here is a short video on how you can ’empty your cache’ in Safari. Note that emptying your cache is NOT the same as clearing your history.