Several BA accounts have been hacked and points have been used, so BA has preemptively drained the Avios out of many BA Avios accounts before more damage could be done.

If you do have trouble logging into your account if your account shows an incorrect 0 balance you can call British Airways at 800-452-1201 to re-verify your identity and regain full access to your Avios. It may take a day for online access to be restored, but if you do need to make a booking now they should be able to do it over the phone and waive the phone booking fee.

HT: dansdeals