I'm having experiencing the same issue and can't figure it out.
Prince is output the "warning: The requested URL returned error: 400" on some of the images. And it appears like it's always doing it on those same set of images. But there's nothing special about them. And I can access these images just fine both on the browser and through CURL.
And here's the weird part. Previouly this is how I ran it: "prince temp/page.html -o pdf/page.pdf" And while I was debuging I went into the "temp" folder and ran it like this: "prince page.html -o ../pdf/page.pdf". And guess what? It worked! But... why? how? But the bad news is that while this worked for "page.html", it started producing the same "400 error" on other page that used to work worked before when I ran it like "prince temp/page.html -o pdf/page.pdf". So this is just weird and doesn't make sense (at least to me).
The apache log file didn't show anything useful. The error didn't any have anything. But I did notice that the access log file occassionally produces weird entries when Prince retrieves documents:
74.208.70.134 - - [12/Mar/2010:13:53:45 -0500] "GET /web/generate_image.php?code=154232 HTTP/1.1" 200 11301 "\x80w\xbf\b\x80w\xbf\bal/lib/prince/etc/curl-ca-bundle.crt" "Prince/7.0 (
http://www.princexml.com)"
What are all those weird characters (\x80w\xbf\b\x80w...)? Is this normal?
Sunny