Okay, so that's working at least.

The "sudo gainroot" shouldn't be asking for a password though, so the next thing to do is check whether the sudoers entry is correct - what's the result of running (as root) the following?:
As for the lock error, you can try checking for applications holding the lock file. You'll need to be root, and have lsof installed (not sure whether it's standard or not - it's in the Nokia SSU repository though), then run:
If that doesn't list anything, I'd also suggest checking rootfs space (df -h /) - it may well be unable to lock the file if there's no rootfs space free.