Problems with upgrade

I recently upgraded my OS to the new Version 10.5.8 and my MB is turning on and off as soon as it starts up. (Upon startup it will turn off/turn on and 5 seconds or so it will repeat). Only after about 10 min (after the computer has warmed up), will my system be fine again....Any ideas?

I read up on another user that was having the same problem, and the thread mentioned to start the system again from the system install DVD...except I was not able to CD that came with the computer....Please help!!

How did you upgrade to 10.5.8?

thru the software update on the apple menu...

ok... since you don't have the install discs, the solutions that I have in mind may be tricky.
I think the first step then, since you mention that after the system has warmed up, you are able to keep it running, is to repair disk permissions (applications>utilities>disk utility), and then go to this link Mac OS X 10.5.8 Combo Update and install this update, and post back with the results.

ok. i will run it all tonight and through the day tomorrow. ill make sure to post the results. thanks!

so far nothing has changed..i am still running into the same problem. i am planning on going to the apple store today to see if they can give me a diagnosis. i will post the solution soon..in any case, thanks for the help!