A little more information from what I've found:

For the versions of the 2.6 kernel that I tested (at least 2.6.15 and 2.6.16.13), the cpqarray driver cannot be loaded as a module. This means that if you are using the 2.6 kernel series, you must compile your own 2.6 kernel with cpqarray compiled in. Most likely, this also means that your distro installation CD must be booted with a 2.4 kernel. If you ignore your advice, you will see in the kernel messages, "cpqarray: Finding drives on ida0", "cpqarray: ida0: idaSendPciCmd Timeout out, No command List address returned.", "cpqarray: error sending ID Controller", etc. I don't know why this happens, but I was able to get around it by booting into a 2.4 kernel or compiling cpqarray into a 2.6 kernel as a built in drive
gah now I'm gonna have to build a stupid iso with the 2.4 kernel or a new 2.6 kernel with no modules. *sigh*