Hello,
I just checked it on my installation running WP 4.4.1, and uploading images directly to the post editor works perfectly fine, so it could possibly be due to a conflict between WP 4.4.1 and your theme or one of your plugins.
Can you try disabling all plugins, switching to a default theme (like TwentySixteen) and checking if the problem persists?
If that fixes the problem, try switching again to your theme (with all the plugins still disabled) and see if it returns.
If it works fine with your theme, try enabling your plugins one by one and checking if the problem has returned. Once you find the culprit plugin, you should notify its author of the issue at that plugin’s support forum, as they’ll be able to help you better with fixing that conflict.
In case you find that the problem isn’t being caused by any of your themes and/or plugins, reinstalling WordPress itself would be a good idea, just to make sure that all your core files are intact and unmodified.
In order to do that, download WordPress again, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel, and delete then replace your copies of everything except the wp-config.php file and the /wp-content/ directory with fresh copies from the download. This will effectively replace all of your core files without damaging your content and settings.
Some uploaders tend to be unreliable when overwriting files, so don’t forget to delete the original files before replacing them.
Hope it helps.
