Help Desktop Backup Password problem

[Tom Conway]

I've spent a couple of hours setting up ADB so I can backup the S3 to my laptop. When I started running the backup I was prompted to enter a password on the phone but I cant remember setting one up. So I cancelled the backup and went into Developer Options to set a password but it keeps prompting me for a password before I set one up. Now, I've either set one up and in my dotage cant remember the darned thing! or the S3 is behaving oddly. Anybody have any experience of setting up this password? Any ideas on how I could round the problem preferably without a factory reset.

Thanks