Just heard about this last night so I wanted to put this out there.
We're aware of an issue with the Bitlocker Drive Prep tool (http://www.microsoft.com/downloads/details.aspx?familyid=320b9aa9-47e8-44f9-b8d0-4d7d6a75add0&displaylang=en) on Windows Vista/2008 with SP2 installations. You'll get an error regarding the "Update does not apply to your system" similar to the issue I blogged about CheckSUR. We will have a new binary out shortly that will work with SP2, no timeframe as of yet.
As a workaround, you can try to do the following to manually install the update:
expand -f:* "C:\Windows6.0-KB933246-x86.msu" %TEMP%
start /w pkgmgr.exe /ip /m:%TEMP%\Windows6.0-KB933246-x86.cab
C:\Program Files\BitLocker\BdeHdCfg.exe will be the tool that you want to run post installation of the package. The GUI version of the tool will still fail to work properly. Use of this tool is discussed more in the following article: http://support.microsoft.com/kb/933246/en-us
What this will do is expand the files that make up the standalone installer into your temp directory and then allow you to manually install them with PKGMGR to the system. I'll discuss in a later blog as to when is a good time to do this and when its not appropriate, but for this update, it should work properly.
UPDATE: We're aware that this is effecting the other Bitlocker tools as well. Thank you for your comments. The updates are being worked on and will be out rather soon. I'll let everyone know when they hit so you can grab the new bits.