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I'm having the common media upload problem where images will fail uploading and send the error. However, this problem seems to have popped up with a change I've made recently because my WordPress site had been running for a few weeks and had no previous trouble with uploading media. It just recently acted up on me and sent me these error messages:

Warning: File upload error - unable to create a temporary file in Unknown on line 0

Warning: Cannot modify header information - headers already sent in /MYPATH/wp-admin/async-upload.php on line 26

“test-image.jpg” has failed to upload due to an error

Missing a temporary folder.

I've made sure that my wp_config file didn't get any blank spaces appended to it, checked my "uploads" folder and set permissions to 777 and also checked the file "async-upload.php" and line 26 had this line: header('Content-Type: text/plain; charset=' . get_option('blog_charset'));

I'm a bit confused on why all media uploading was fine and randomly started pushing this error. Is this something that may fall back on my host?

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@Joshua Abenazer Perfect! My current "upload_tmp_dir" was still set to a previous location locally. – cqde Dec 2 '11 at 8:06

Have you added any function or method to your working directory if so buffer your output by adding ab_start() on top of it and add ob_end_flush() bottom of your function, this will resolve your problem, if am wrong let me know what exactly happened.

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