I upgraded one site from 2.8 to 2.8.4 and the file permissions of folders are mostly 755. The files are 644. So for the theme 755 and 644 for the files in that folder including in the images subfolder. I have tried other permissions on some of the files. The header image of the theme won't display. I will retest that them elsewhere but it does work on other hosts and has worked for 2+ years on this one.
I did try "Assign 766 recursive permissions to wp-contents folder" that stopped the site working altogether.
The second issue is that images on the uploads folders /wp-content/uploads/2009 are not displaying at all.
folder settings are 755. and file settings - mostly photos are also set at 755. I have tried the reset to 644 or something else and only get "Operation not permitted"
That looks like a separate permission error so asking the host about that one. I suspect that if I can make all the images inside the upload folders rest to 644 then we will be able to see them again.
But that isn't working for the theme image header file.
I'm going to test on another host and try deactivating all plugins - however this is an old site and everything has been working well until the last 2 upgrades. 2.8.2 & 2.8.4.
I do the upgrades manually on this site. My topic is not resolved - but not sure how it is different to the above scenarios.