@takayuki: Details are sporadic, but imagefill has been the subject of several bugs fixed between 5.2.4 and now.
https://bugs.php.net/bug.php?id=51128
https://bugs.php.net/bug.php?id=51671
https://bugs.php.net/bug.php?id=60160
Admittedly none of these specify my exact problem, but it sounds like it’s probably the same root cause. In all cases, imagefilledrectangle() has worked as a substitute, and in one of those, was the suggested workaround until the patch.
@takayuki: My server runs 5.2.6 and I’m using the most recent version of WordPress (3.3.1), and I encountered the problem there anyway. I’m not completely sure which version this bug was fixed in, but it’s still in circulation.
