This happened on my account - "Unsanitary"
I was trying to talk in the chat but it wouldn't let me.. so I asked over yell if the chat was broken and somebody told me the same thing happened to them(they couldn't talk in chat, private message, couldn't join Friends chat) - and told me to restart my client.
I was training Smithing in a medium dungeon, I was waiting until i was done to re-log so I didn't lose progress in the dungeon.
When I exited the dungeon and logged out, I logged back in back at priffdinas and I was set back 20 smithing levels and 9 dungeoneering levels.
I was at 93 Smithing and 92 Dungeoneering (roughly 4 hours of work), and when I restarted my client I was set back to 73 Smithing and 85 Dungeoneering.
I also lost all of the tokens I earned in that timeframe - pretty livid so i'm staying off until I get a response :/