Win XP Hangs after Splash Screen (PointSec Loaded)

Question

I have a lenovo t400 laptop, that has Pointsec encryption (6.1.3) ,and WinXP loaded on it.
I ran the Think Vantage Lenovo update tool which downloaded and installed a number of updates - as I hadn't run it for ages.
Now when I try to start the computer it hangs after the XP splash screen is displayed. The screen simply goes black.
I have tried the various Safe Mode options (include VGA Mode, and start with last successful configuration) without luck. They also fail to boot.
The flow is:
Power On, PointSec Authentication Screen, Win XP Splash screen, then a black screen
I have successfully got into the system using UBCD4Win with the pointsec plugin loaded, this loads a WinPE type environment via a USB stick and allows me to access the C: drive unencrypted (as I have authenticated with Pointsec).
I'm really stuck for ideas as to which of the update is causing the problem, and would love to hear some suggestions on how to fix this situation.
Additional Info:
The last few lines in ntbtlog.txt is:
Did not load driver Direct Parallel
Did not load driver SM bios service
Did not load driver SM bus service
Loaded driver \SystemRoot\System32\Drivers\Cdfs.SYS
Looking in:
c:\Windows\$NtServicePackUninstall$
it looks like Service Pack 3 has been installed:
The file: spuninst\spuninst,inf shows:
NtServicePackVersionText = "Service Pack 3"
NtServicePackPreviousVersionText = "Service Pack 2"
Solved!
Go to Solution.

Answer 1

Fixed!!!
The problem was the lenovo updates (most likely culprit being the video driver I presume).
Using UBCD4Win with the pointsec plugin I was able to
* get  access to the decrypted c: drive
* Manually rolled back the updates to c:\windows\system32 and c:\windows\system32\drivers
Original files were found in places like: c:\windows\system32\reinstallbackups\008\DriverFiles
* Finally I had to roll back the registry updates that the updates did. UBCD4Win provides a tool to do this:  Registry Restore Wizard. It basically just looks in the System Restore Directory c:\System Volume Information and lists all the available Restore Points (thankfully the Lenovo updates mark a restore point before they run). You can also do this manually using the following instructions:
http://hypography.com/forums/tutorials-and-how-tos/17193-xp-recovery-instructions-for-ubcd4win.html
This done the system booted successfully.
I most definitely will be staying clear of pressing the big blue button from now on. That was a real nightmare to fix.