Sync to Dropbox was working, now not

As the title says, I had set up a rule that synced my nested folder structure of documents on my hard drive to Dropbox and all worked great for a while. It has since stopped working for a reason I can't fathom. Below is the extract from the log:
2013-11-15 12:44:57.842 hazelworker[5586] [Error] Could not sync file/folder: Could not sync file/folder at Documents in Dropbox to /Users/stephencourtney/Dropbox/Documents in Dropbox.
2013-11-15 12:44:57.842 hazelworker[5586] Sync returned error status: 23
2013-11-15 12:44:57.875 hazelworker[5586] Done processing folder Documents
2013-11-15 12:44:58.757 hazelworker[5591] Processing folder Trash
2013-11-15 12:44:59.814 hazelworker[5591] Done processing folder Trash
2013-11-15 12:45:10.270 hazelworker[5599] Processing folder Downloads
2013-11-15 12:45:12.370 hazelworker[5599] Done processing folder Downloads
2013-11-15 13:08:21.352 hazelworker[5633] Processing folder Desktop
2013-11-15 13:08:23.379 hazelworker[5633] Done processing folder Desktop
2013-11-15 13:08:36.443 hazelworker[5634] Processing folder Action
2013-11-15 13:08:38.541 hazelworker[5634] Done processing folder Action
2013-11-15 13:08:51.365 hazelworker[5635] Processing folder Documents
2013-11-15 13:08:53.633 hazelworker[5635] Documents in Dropbox: Rule Sync to Dropbox matched.
Can anyone tell me (in relatively plain English) what I need to do to get this valuable rule working again? thanks!
2013-11-15 12:44:57.842 hazelworker[5586] [Error] Could not sync file/folder: Could not sync file/folder at Documents in Dropbox to /Users/stephencourtney/Dropbox/Documents in Dropbox.
2013-11-15 12:44:57.842 hazelworker[5586] Sync returned error status: 23
2013-11-15 12:44:57.875 hazelworker[5586] Done processing folder Documents
2013-11-15 12:44:58.757 hazelworker[5591] Processing folder Trash
2013-11-15 12:44:59.814 hazelworker[5591] Done processing folder Trash
2013-11-15 12:45:10.270 hazelworker[5599] Processing folder Downloads
2013-11-15 12:45:12.370 hazelworker[5599] Done processing folder Downloads
2013-11-15 13:08:21.352 hazelworker[5633] Processing folder Desktop
2013-11-15 13:08:23.379 hazelworker[5633] Done processing folder Desktop
2013-11-15 13:08:36.443 hazelworker[5634] Processing folder Action
2013-11-15 13:08:38.541 hazelworker[5634] Done processing folder Action
2013-11-15 13:08:51.365 hazelworker[5635] Processing folder Documents
2013-11-15 13:08:53.633 hazelworker[5635] Documents in Dropbox: Rule Sync to Dropbox matched.
Can anyone tell me (in relatively plain English) what I need to do to get this valuable rule working again? thanks!