I have to say that i had a very similar experience on a 400mhz tibook w. 1gig DRAM. • Installed the two security updates and after restart experienced a video screen freeze halfway through the startup blue screen and the log in screen. • On restart never got beyond a grey screen. • After resetting hardware button, achieved a blue screen with an endlessly spinning pinwheel (not beach ball). • Starting in 'Safe' mode led to kernel crash with unix lines and ten language box in center. • Could not start in target disk mode. • Could not boot from external firewire drive. So it's off to Tekserve (great guys) and computer hell. Their diagnosis: • 1Gig of memory failed (both upper and lower) • Faulty Logic board which on 'Shut down' will not let you start back up and show any video without resetting hardware reset button. (On my model, it is external on the back of the case). However, if you choose 'Re-start' in stead of 'Shutdown', no problems. • Some inevitable corruption to the hard drive (overlapping blocks, etc) that was non-repairable requiring pulling off data and re-formatting and restoring data. This requires a round trip to Apple Depot for the $395 tier one servicing. (Hmm, should I kick in the extra money for tier two servicing and get the cracked hinge, screen marks, separating screen case, etc addressed, or wait for that mythical G-5 book?) ANYWAY, after reading all the replies to this post, the best advice that anyone should give you is to BACK UP YOUR HARD DRIVE RIGHT NOW WHILE YOU STILL CAN because you certainly have a hardware/software issue that will take your hard drive down for the count very soon now, (if it has not done so already). One can speculate that the security updates had something to do with this but it is highly unlikely! This was my first thought also. However, you probably have a hardware issue, either memory and/or logic board, that is starting to act up. Inevitably, this will cause corruption to the data written to your drive. The first symptoms will be the ones you are describing affecting the operating system, start up and overall performance, spinning beachball, etc. Eventually, when you are writing some critical data file, the corruption will occur obliterating and overwriting your original file. Did I say back up while you still can? I expect to be without my computer until Monday. (That will be one week. God, withdrawal is hard!) But, I am up and running, thanks to Carbon Copy Cloner, on my wife's Bronze Keyboard G3 Power Book, while my TiBook round trips to Apple. (I swapped her internal drive with my external drive back up). So back up, my friend and take your book down to someone you trust to check out your memory and logic board. Peet H. Peet Foster-Design 32 Bramble Lane Riverside, CT 06878 (917)975-3731