Open New Plots - Only with GB?

Right now i have only 4 plots left to open, last one cost $74M, and the next one will not allow me to use cash to open! My understanding was that this is only the case for the last 2 plots as the max bank upgrades (max is $96M) would not cover the costs to open.

Is this a bug?
Answered here : http://sublinet.com/fr/forum/topic.php?server=39&id=14832#post-109896