Encountered a similar issue upon my login this evening. I was concerned that I might’ve been hacked, but it seems unlikely because;
1. All my characters are in the exact same place I left them
2. No character is missing any gear or karma
3. I have no mail or people I don’t recognize in my contacts list
4. No logins not corresponding with my own IP address listed in my account
5. Only the characters that have used the Trading Post have been affected by missing gold
I hope something gets worked out. I submitted a support ticket, but I expect it will be a few days before I hear anything.