Currently I can see the following opportunities:

b7USD => britcoinGBP
1. Buy 1 BTC at b7USD for 16.2 USD
2. Sell 1 BTC at britcoinGBP for 16.95 USD
3. Win the difference (0.75 USD)

b7USD => thUSD
1. Buy 1 BTC at b7USD for 16.2 USD
2. Sell 1 BTC at thUSD for 16.9 USD
3. Win the difference (0.7 USD)

b7USD => bitomatPLN
1. Buy 1 BTC at b7USD for 16.2 USD
2. Sell 1 BTC at bitomatPLN for 16.72 USD
3. Win the difference (0.52 USD)

I am not sure that the "window is now closed".
How should that have happened? Someone using an automated arbitrage software?