User gets error message upon login – "You attempted to edit an item…"

One of my site administrators has been getting the message “You attempted to edit an item that doesn’t exist. Perhaps it was deleted?” when logging in, instead of seeing the dashboard. This has been occurring in her usual browser only (she can get in normally using a different browser), and flushing cookies and cache seems to have no effect. As far as I know, other users are not having the same problem, and I have not had the same issue myself.

When she gets this message, she is able to go to the site home page, log out from the menu bar, and then log in normally. But this morning it happened again.

What would cause this message to appear upon login, and is it just a weird browser cache issue or is something more serious going on in the database?