After not touching my WordPress site for more than 3 weeks, I returned to work this week and updated to 3.5.2. Since then I've encountered multiple issues:
1) After attempting login at /wp-login.php, I get the notice that "The connection was reset" and to "try again later." Thinking this was a server issue, I contacted my host provider (GoDaddy), and they told me to give it 24 hours as the server was just "really busy." They also told me it could be happening because my site is slow. However, I had not been experiencing a slow site previously, and no content has been added since accessing it regularly early last month. It has also been more than 48 hours since it started.
2) I've tried re-installing the upgrade, replacing upgrade.php (from File Manager in GoDaddy since I can't access through FTP now, either), disabling plugins, emptying my cache, restarting the browser (Firefox), etc. yet I keep getting the screen at various points when I'm clicking around on the admin side. (This is not browser-specific. Same thing happens with multiple browsers.)
3) If I'm lucky enough to log in without getting the "reset connection" screen right away, I then can't upload new images to posts, pages, or portfolio items. It starts the upload, then says "An error occurred in the upload. Please try again later." However, if I navigate to the Media Library afterwards, I'll see the image I just tried to upload 3 times. (In other words, first it tells me it fails, then I see 3 copies of it in the library.) In addition to that, if I try to upload an image from the Media Library, it shows up as empty so there's nothing for me to choose. I can neither upload from my computer nor the Media Library now.
I'm a designer, but I've been working with WordPress for quite a while and never encountered this issue. Any suggestions are appreciated! I have no idea what the source is, so I don't know where to ask for help.