What version are you using, and does the problem stop if you stop and restart iJ?

You need to go back to the Live Journal site and reverify your age—possibly also your email address, if that has changed—using their chosen method. That has completely solved the problem for me.

Log on to the web site—through your browser, not through iJournal—and try to, for example, edit your personal information (that's what did it for me)—basically, try to do any one of several operations that are part of using your account—and if your age needs verification, the web site will take you to the process that you have to go through. Note that you will need a second email address (different than the one you used to register) and a credit, or check card (you might see a charge of $0.01 to the card; I think that is just to access the relevant information for verification). As part of the process they assume that you are actually a child who needs their parents' approval, and if you are not a child (maybe, like me, your parents are both dead for years) they give you no way of getting through the process without committing a little deception along the way. This also leaves a loophole for those children who do have credit cards and multiple email accounts. Apparently Live Journal has no problem with this as my attempts to convince them to change the process have met with no success at all.