Requiem 1.8.8 is the latest version I know. Please try to use it instead of Requiem 1.8.1.

Requiem requires iTunes 7.6.2 or LATER in order to work. It will NOT work with any previous versions!

Requiem 1.8.8 seems to work with iTunes 8.1, but not iTunes 8.1.1 or higher.

If you buy something with a version of iTunes that isn't supported by the latest Requiem and it's not able to be decrypted with the keys in the cached keystore, try the following:

1. Deauthorize your machine
2. Uninstall non-working iTunes
3. Install previous, working iTunes
4. Authorize the machine
5. IMPORTANT: PLAY the file you want to decrypt!!
6. Decrypt with Requiem which should add the new key to the cached keystore
7. Re-upgrade to latest iTunes

AddOn: Requiem 1.8.16 is available.