Increase length of Upload Info Fields
First, make a backup of your CMS database under the backup and restore menu before making any changes.
Then, the uploads table is hidden in the "Section Editors" list but you can edit it by typing in the table name directly like this:
Modify info1, info2, etc and at the bottom under "Advanced Options" set "MySQL Column Type" to MEDIUMTEXT
Let me know if that works for you.