[TYPO3-english] Weirdest bug i've ever seen - Imagemagick not recognized when conecting to BE from a certain ISP

[Christophe Stadler]

One of my students is working on a typo3 website installed at my hosting
provider. I have typo3 installed several times on this server and everything
works fine. When working from my offices or from an internet café everything
works as expected, we have tried several machines with different operating
systems and browsers and there is no problem.

However, when my student is at home (connecting through the ISP Fastnet) he
has a weird problem. When he goes to the InstallTool>Basic or Image
Processing the system reports that Imagemagick is not installed and
ImageProcessing tests are skipped. Because of this he has a lot of problems
when working in the backend, sometimes all the thumbnails disapear and
options he sets for the images (width/height/clickenlarge/url) don't work.

But it gets weirder, when he connects to another typo3 install (same version
4.3.3 but on a different server) he doesn't have this problem, it only
occurs on this one particular typo3 install (nothing special about this
install, pretty much out of the box with Templavoila as only extension) ...

I suspect the problem to his connection at home, the only thing that is
different there is the internet accès (router/connection), with the same
machine (his Macbook Pro) it works everywhere except at home.

How can this be ? Imagemagick and Typo3 are installed on the server so what
has his internet connection got to do with anything ? He doesn't have any
problems with any other website, even other typo3 installs.

The typo3 site works perfectly from 6 different machines and different
networks/ISPs, Mac or PC, with Firefox, Safari, Opera, IE7, IE8 .. On every
setup everything works and reports Imagemagick installed ... Just when he's
at home it doesn't ...

I'm out of ideas ...