Hi Peter,
I had non-alphanumeric characters in the filename of the screenshot attachment and it was rejected by your ticket system.
Thanks for that information, we're using Akeeba Ticket System, I'll make sure to pass the issue along to them.
As for your main issue, we have found that the error is not happening in sh404SEF but in Google Chart library. It updated to a new version and they are experiencing the problem, under undertermined conditions.
I have made a workaround by forcing sh404SEF to use the last working Google Char version insted of the latest one. You can find that version as usual in the development versions download area .
Or you can wait until they fix the problem and release an update, which sh404SEF will use as soon as they release it.
Best regards
Yannick Gaultier
weeblr.com / @weeblr