Insufficient permission to upload

When I make edits to a document and save it, I will get an error message that says "You have insufficient permission to upload".  Immediately after, another error message follows listing the box folder name and saying that the document could not be updated.  This does not happen on every document but some.  The document will update on MY computer but when co-workers open the document in the file, they will not see the edits made.  Any thoughts?  Thank you