It is always possible that a new signature could block traffic. But applying any update (signature or software) will NOT change settings you have made to existing signatures. Once you disable a signature, it should always stay disabled.
I had this same problem when trying to drag and drop an RSS feed gadget to a dashboard. I was able to get it to work by clicking the add button instead of doing a drag and drop. It still displays the error but it adds the gadget. Once the gadget has been added to the dashboard you can modify it by clicking the wrench icon.