Hi Dennis?
I'm assuming this is related to your QA 6628 and Blitz log at QA 6632?
Thanks for the info above - it seems that the 'black thumbnails' is a client-side issue.
Do you have the client logs for the 4.4.7 Insight for when you're seeing black thumbnails or "not a valid image" when opening an image?
What OS (and version) are you running Insight on?
You said that "many" of the thumbnails are black. Is there anything different about the black ones? E.g pixel type, size, number of channels etc?
I wonder if the web jpeg issue in QA 6628 is the same as the Insight 'black thumbnails'... Is the jpeg download failing on the same images that are displaying OK in the web main image viewer?
I've created a ticket for this to try and collate all the info on this issue:
https://trac.openmicroscopy.org.uk/ome/ticket/10838