ok, if it was me, id prob try re-installing the forum using the zip file from the smf website to be sure that all the files are the most recent but to do this you will need to upload via FTP & you would also need to setup a MySQL database for it, so I wouldn't recommend it if your not sure how as you would also want to backup & then import the forum data or you would lose everything! :(
Other than that, I'd prob do what the dev said, disable the wysiwyg editor (even if only for a few days to see if the problem goes or still persists) then when v2.1 is released, just update to that :)