Image Uploader problems in 3.0.1

Hi everyone:
my image uploader works like a charm except when it comes to editing thumbnails. I get a broken image icon instead of the image:
https://www.radhanathswami.com/wp-content/uploads/wordpress-thumbnail.jpg

I read this thread but nothing works and it strikes me as outdated:
https://www.ads-software.com/support/topic/25-imagemedia-uploader-problems?replies=1

Under Super Admin > Sites > Edit Site, I set “My Fileupload Url”, “Upload Path”, and “Upload Url Path” to:
https://www.radhanathswami.com/wp-content/uploads
I also tried “/wp-content/uploads” and with a trailing slash at the end but nothing worked.

Then I tried setting the “uploads” folder permissions to 777 as per this advice:
https://www.ads-software.com/support/topic/image-uploader-new-problem?replies=3

No dice. To repeat, all my images display without a hitch, I only encounter problems when try to edit them. This feature has worked for me in the past (circa 3.0), I can’t recall when I messed it up. My site is also hosted on a crappy server, so I don’t discount that as a possibility.

Suggestions anyone? Thanks a lot,
-JP