Bitlocker event 24620

Überprüfung des verschlüsselten Volumes: Die Volumeinformationen auf "" können nicht gelesen werden.
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Windowstaste + r 
eventvwr.msc

Laufwerksbuchstaben, die einem Card-Reader zugewiesen wurden?
use gpedit.msc
Use of Readyboost?
Verwendung von Paragon Backup SW?

http://technet2.microsoft.com/window....mspx?mfr=true
Resolve
Use the BitLocker Repair Tool

BitLocker entered recovery, and a user has successfully completed the recovery process by using a recovery key (stored on a USB flash drive) or a recovery password (entered manually at the recovery screen). The most recent recovery session happened because volume information could not be correctly retrieved from the volume metadata.

Although data corruption can occur, it is rare. Data corruption can be caused by hardware failure or physical damage.

If a volume is damaged, you can use the BitLocker Repair Tool to salvage any recoverable data. Using the BitLocker Repair Tool is an advanced procedure that should be performed by an experienced administrator.

For more information about using the BitLocker Repair Tool, see "How to use the BitLocker Repair Tool to help recover data from an encrypted volume in Windows Vista" in the Microsoft Knowledge Base at http://go.microsoft.com/fwlink/?LinkId=99556.

Verify

To verify that BitLocker has started successfully:

1. If the computer is not running, start the computer.
2. If BitLocker has been configured to use a USB flash drive, insert the USB flash drive. If BitLocker has been configured to use a PIN, enter your PIN when prompted.
3. Verify that Windows Welcome Screen, Logon Screen or Desktop appears. This indicates that BitLocker has correctly unlocked the Windows operating system volume.
4. Log on to Windows and access any data volumes that are encrypted with BitLocker.

Note: Data volumes can be configured to be automatically unlocked or to require manual unlocking.

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http://www.id.uzh.ch/dl/bs/vista/ein...umentation.pdf
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Source
Im Systemregister überprüfen unter
HKLM\SYSTEM\MountedDevices
, ob der o.g. GUID gelistet ist. Falls ja, sollte weiter unten auch ein Laufwerk (z.B. DosDevices\C:) dafür gelistet sein. Diesen kannst du erkennen indem du den Byte Wert vergleichst. 
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Wenn Ursache des Problems, dass die Systempartition offline war
Beheben mit Windows7 StartDVD
diskpart.exe 
select disk 0 select part 1
online volume