So before the F2P build got ported over to live I had 6 characters made and still had the ability to create 2 more characters. I just went to make a new character and discovered I no longer have open slots. Where they lost because F2P only allowed only 6 per player (the base amount, +lifer +whatever else it was)? Remember reading that we wouldn't be losing anything we already had with the crossover, so what happened?
Can't say I know what's wrong with your slots.
But it appears there were a few cases where people had more slots than they should have had due to a bug.
When the bug was corrected the slots disappeared.
You might want to take a look at this thread where a DEV answered a few questions regarding the slot issue: