iTunes encrypted backup

Hi,

today I realized the "Encrypt iPhone backup" option is turned on. I am very sure I never enabled this option. May this have something to do with recent 3.1(2) upgrade?

Also, I can't get the password into it, as I can't remember I set any! I tried every possible code I've ever used on the iPhone, but nothing. Also, it's not stored in the Keychain access, which makes me thinking it's a glitch (I normally store all the password in keychain).

I know Apple officially documents you can't restore it.

Was someone affected by this? Is there any workaround? I would really need to recover my backup for future needs, can't afford to stay with backups I can't use. This is a loop since to remove that setting I would need to do a fresh installation (recovery mode) but I can't use the existing backups...

Thanks

Davide