Ipoker has a new 4 HU tables max now. Confirmed by expekt support. You can only open 4 empty HU tables at a time, but you can sit down at tables where there's already someone sitting.
This is the mail they sent me when i asked about it:
Thank you for contacting us.
As we spoke about over the chat. Here is some additional information:
New Feature: Limitation of Seats for Heads Up Tables
Some players sit at a number of heads up tables waiting for an opponent to join them. If they do not wish to play with the opponent who joins them, they can sit out, and since they have not left the table, a stalemate will occur. Eventually the situation could reach a point where there are no open seats remaining for a certain stake. To counteract this, we now only allow players to sit at a limited number of Heads Up tables without playing (i.e. remaining in sit out status). This default number per network is 4.
If a player tries to join a heads up table while he is already seated at the configured number of heads up tables, the following message will be shown: Sorry, This seat is Currently Unavailable, Please try again later.
Heads up table limitation players can only open 4 empty tables at a time, player then can open additional tables that have players already sat waiting to play on.
As you can see from the above this does not stop players playing at tables but does prevent players stalemating the tables through sit out..."