That did the trick installing php5.3. Thanks!
Up until Ubuntu 9.10 the gd-package provided by the debian installer is the original gd package that does not have the proper image rendering...
After first forgetting to sed -i 's_\(--with-gd=shared\),/usr\( --enable-gd-native-ttf \\\)_\1\2_ debian/rules, I tried a recompile on a 64-bit...
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