i reported that problem in the beta too but i didn't get an answer. now i have it too.
and the problem is: i have more than 500 workers and had only one OP. the OP was taken and that way the number of my workers became above the capacity. in the old client in such case you were able to just build another OP but here it's not possible and the following msg is displayed: ERR_YOU_ARE_OVER_CAPACITY.
is that a bug or is it ment to be that way? if it's ment to be that way then why is it so?