2.7 Uploading Images: Failed to write file to disk.

Yup, I’m experiencing the same thing here using WP2.7, Firefox 3 and WinXP. One thing you said, though, made me think. The flash uploader on my machine stopped working when I upgraded Flash to v10. Maybe going back to Flash v9 will solve the “Failed to write…” error too. Will test to find out…

Well, the Flash Switcher plugin for Firefox has not been updated for the latest release, so I can’t test it now. I did notice, however, that the file I was trying to upload had a similar name to previous upload, so I deleted the prior and the second upload worked fine. Lame, but it resolved the issue (kind of) for me…

Flash uploading with FF3 (on XP) does not work for me either. I am taken to the wp-admin/login screen after attempting.

Have you checked the permission on the wp-content/ directory if you haven’t uploaded yet, or the wp-content/uploads directory, if you have? I personally create the wp-content/uploads/ directory manually, so that the WP install stays mainly unwritable by the webserver.

For FreeBSD, I use

# chown www:www uploads
# chmod 755 uploads

Your user and group may be different on another platform.

(I’ve seldom had the Flash uploader work for me either.)

Today I started experiencing this issue as well after successfully uploading several photos. I did an extensive search on this forum and Google I was amazed to not find a clear resolution. This lead me to searching through the WordPress core files for the error message to see what was going on. The error message seemed to be triggered after the file was uploaded to the temporary directory where php stores the newly uploaded file. I did not have access to this directory, so I contacted my host and they were able to repair/remove the temporary files in the directory. This immediately resolved the issue for me and I hope this helps resolve it for all of you.