Do site da TrueCrypt:
When the system partition/drive is encrypted, the system cannot be upgraded
(for example, from Windows XP to Windows Vista) or repaired from within the pre-boot
environment (using a Windows setup CD/DVD or the Windows pre-boot component). In such
cases, the system partition/drive must be decrypted first. Note: A running operating
system can be updated (security patches, service packs, etc.) without any problems even
when the system partition/drive is encrypted.
Falta de um aviso ... Eu nem sequer pensei nisso.