U n S shaped slot antenna for WLAN on CST

Dear all...
i m having a problem using CST microwave studio....
I have designed a dual band antenna for WLAN...
Its working for the 802.11 a/g standards...
But when i tried to simulate it for the 5 to 6 GHz band, there comes an error and the whole CST window get hanged....
Is there any possible solution for this problem?
sometimes it simulate for other designs but not specifically for my design...
May be the mesh cells are too large to simulate the design....

kindly help me out...
i,ve to submit my project on the 17th of this month..