kernel_task help

I installed 10.5 (Leopard) on my G4 733 Mhz (after minor tampering with the install package, just switched a boolean FALSE to TRUE).

Everything works fine after startup, but once I sleep the computer and wake it back up, kernel_task starts using at as much CPU runtime as it can, as in past 90%.

Any ideas? I've tried a fresh install (wiped disk), but to no avail.

Thanks!
-Peter

edit: Problem solved. Turns out installing it from a another computer with target disk wasn't so good an idea as I'd thought.
After installing a DVD drive, things started going smooth again.