Today I installed php5-curl via apt-get on our Debian linode.

When that package installed, it somehow broke GD functionality on our Drupal site:

Warning: imagecreatefromjpeg(): 'public://sports_article/DVP4965023.JPG' is not a valid JPEG file in image_gd_load() (line 237 of /var/aegir/platforms/ehsa-1.5.3-drupal-7.8/modules/system/image.gd.inc).

New images won't generate, etc.

As near as I can tell php5-curl introduced some conflict with libjpeg but beyond that I am completely stumped so far.

Can anybody point me in the right direction?

Are you absolutely positively sure that curl is the problem? I have to ask because many people forget that they also made other changes since the last time they restarted Apache.

Uninstall curl, restart Apache -> Does it work now?
Reinstall curl, restart Apache -> Is it broken again?

Also, the non-standard "public://" scheme looks like a nasty bug waiting to happen. I haven't touched Drupal for a while, though. Where is this file actually located?

Having said that, php5-curl sucks ass. It used to crash when combined with php5-pgsql. I avoid it like the plague since then, but sometimes there's no other choice.