tikiwiki.org runs on the debain platforum and the image galleries had to be moved to uk.tikiwiki.org because of a debain problem. You might be in a similar boat.
Although If your using imagick for graphics the thumbnails for GIFs should work.
You could also try setting your memory limit to 32Mb and possibly install Turck-MMCache to optimise and speed up the code.
Also whats your version on PHP? 4.x is open to be anything 4.1 to 4.3.6 and some tiki features dont work with early 4.1 See the InstallTiki page for a link to setup guides and TIki requirements
Apart from that Im not sure. I'm on Fedora Core