There is no device /dev/hdc anymore on kernel 2.6.18-1.2200.fc5. Also creating the device manually doesn't work. However it seems to be detected, since it appears in the output of dmesg, as well as hwbrowser. On the other hand hal-device-manager shows an "IDE device (master)", but no child to this. Rebooting to the previous kernel 2.6.17-1.2187_FC5 restores the device and everything works as it should.
Created attachment 139390 [details] Output of dmesg for kernel 2.6.18-1.2200.fc5
Created attachment 139391 [details] Output of lshal for kernel 2.6.18-1.2200.fc5
Problem solved. I had "options ide-cd dma=1" in my modprobe.conf, which seemingly doesn't work anymore with 2.6.18.