We've found that many librarians are confused by the term "locked" being use for budgets. It would make much more sense to use the term "disabled".
Hm, have been thinking about this, I think disabled would mean that it cannot be used anymore at all, while I think the feature is meant to only stop people from changing the funds after initial creation (like changing the amounts). From the help file: Locking a budget means that Funds will not be able to be modified by librarians So 'locked' seems clearer to me then 'disabled', but we should probably check how the feature is implemented.
Closing, please reopen, if you disagree. See also: bug 23524 and bug 22786 for some newer developments.