After moving my Drupal 6 websites to another hosting provider, I got an error message every time I have to update a module. It says:

An unrecoverable error has occurred. You can find the error message below. It is advised to copy it to the clipboard for reference.
Please continue to the error page
An HTTP error 0 occurred. http://johanv.org/update.php?id=18&op=do

The problem has probably to do with Drupal issue 1046682, but I don't understand how I can fix it.

But after a whole lot of Googling, I found a stupid workaround for this problem. You can run the update script using Internet Explorer. The problem only shows up with Firefox and Chromium. What a fail.