There's an issue with Seagate Freeagents with the drive's firmware, which when it shuts down due to being unused for a certain amount of time (fifteen mins, but I've heard less on occasion), will power down. Normally, what you'd expect is that if the drive has powered down, it'll wake up after receiving a signal to be used, but this doesn't happen properly with kernels prior to 2.6.24 with that Seagate drive. I notice that Mandriva 2008 shipped with kernel 2.6.22, which would be prior to the working kernel version I mentioned.
My suggestion would be either to upgrade your kernel to a newer version that supports the fix, upgrade your distro to a newer version (which should give you a kernel beyond the fix), or write a cron job that reads the disk every few minutes (downside is that the drive will always be running, but that could also be a good thing, depending on what you want the drive for).
I have a similar drive to yours, and the drive works fine with my Debian Lenny 2.6.26 kernel. It'll power down, but when I want to access it, it'll spin right up again.
Oh, below are some links to the problem and hackish solutions. Hope they're useful to you.
Diane Trout - FreeAgent Drives