Problem now resolved. After I replaced the folders you mentioned I did regain my “use visual editor” option, but unfortunately the visual editor was not working. After much head scratching and searching around I found this solution:
https://www.ads-software.com/support/topic/166212?replies=3
Removing the files from wp-content/uploads/js_cache did the trick. I also looked at the WPLANG variable in wp-config and lo and behold its value was ” ” instead of “en”. I fixed this also. Everything is working fine now. Looks like Filezilla wasn’t the culprit after all…this time!