You’re welcome, Brad.
Okay, I haven’t fixed it… but I wanted to post what I did next to save you some angst. Usually when I get an almost-functional update I just go back and manually reinstall, following the instructions here on www.ads-software.com. So I FTPed in with Filezilla, deleted the wp-admin and wp-includes folders, and replaced them with the new ones from a fresh download of version 4.0. I also replaced the root directory files, but didn’t touch the wp-content folder as there are no changes there.
At that point, things got worse. I now couldn’t access the site at all, and was seeing this error:
Warning: require_once(/home/content/xxx/html/wp-admin/includes/image.php) [function.require-once]: failed to open stream: No such file or directory in /home/content/xxx/html/wp-admin/includes/admin.php on line 28
Fatal error: require_once() [function.require]: Failed opening required '/home/content/xxx/html/wp-admin/includes/image.php' (include_path='.:/usr/local/php5_3/lib/php') in /home/content/xxx/html/wp-admin/includes/admin.php on line 28
I checked my files list and sure enough, the file.php file appeared to have copied over, but wasn’t there. I tried copying it a few more times, and it gave me a successful transfer message each time, but didn’t appear in the wp-admin/includes folder I was trying to copy it to.
I called GoDaddy tech support at that point, and the tech guy there had the same experience. Turned out we were both using Filezilla, and I noticed that in the connection log it was reporting the file as MALWARE… so it seemed to be killing it. I’d already emailed the GoDaddy guy the file, and so he tried using another file manager to put it in place, and that seemed to work. Meanwhile I’d noticed at least three files “missing”, so I told him I’d take it from there, as he was out of suggestions.
I used GoDaddy’s file manager to copy over:
file.php
image.php
plugin.php
All three were referenced in the wp-admin/includes/admin.php file that was mentioned in the error message above, and all three were missing (even though I’d copied them in with Filezilla). Using the GoDaddy file manager, I was able to get them in place.
Okay, that took care of the ugly errors and I could log in. I still couldn’t use the Update feature, so I went back to GoDaddy’s file manager (in Chrome, ’cause it won’t let you copy folders in Firefox). Redid the whole manual install again in case other PHP files had vanished. STILL can’t use Update.
I was also getting weird errors editing posts – for example, I couldn’t add tags. I disabled the Comprehensive Google Map Plugin and that was resolved. However, Update won’t work even with the fresh install and all Plugins disabled.
At this point I’ve decided that since I seem to have all necessary functionality back (just not the convenience of the Updates section), I’ll leave the struggle for a few days and see what the smarter folks on here come up with. If anyone wants to take a look, my client’s site’s at https://dietmdhawaii.com