WordPress 2.5 image upload error

I couldn’t upload images since I upgraded to WordPress 2.5.
All I got was an HTTP error, very strange.

WordPress 2.5 - image uplaod - HTTP error

I hoped that the WordPress 2.5.1 update would fix this problem, but it didn’t.
Luckily there are people who also had this problem, and know who to fix it:
wordpress 25 image upload error wordpress fix

I can’t explain what it does, but now I can upload images again 🙂