Various issues since transfer to MySQL5

I started having issues with my self-hosted WordPress blog, and I believe it dates back to when I transitioned from MySQL4 to 5.

Since then, I’ve had various issues uploading pictures, both through the website and through the iPhone app. It now appears there is a size restriction when uploading photos through the website. Despite my best attempts, nothing I do seems to fix it. I just get an error message when uploading pictures.

And the iPhone routinely locks up when I attempt to upload a picture, only to find it’s available in the Media Library when I check on the actual website.

I’ve also noticed that automatic updates no longer work, for anything – WordPress itself, plugins, themes, etc. Anytime I try the automatic update, it just sits on the window that reads, “Downloading update from…”, but it never moves past that. When I FTP to my site, I can see the files have been downloaded. They just never install.

Any ideas on what the problem could be? Do I have a permissions problem? Did I miss an option when I exported the MySQL4 files then imported them into the MySQL5 database?

Any help would be much appreciated. Thanks in advance.

Sean