hfss error in stitch module

Hi ... i have to simulate a single cell , which is composed of a very small outer membrane and inner cytoplasm , basically membrane is a spherical shell of very small thickness d = 8 nm, ε=11 and conductivity =6 mS/m , and cytoplasm is a sphere of r = 4 micro meter ... when i simulated this structure exiting it with a plane wave and enclosed with an lamba/2 air box (f =2.2 Ghz) , meshing fails .. i get an error saying ....
[error] Mesh generation has failed. Specific details may be found in Modeler>Model Analysis>Show Analysis Dialog>Last Simulation Mesh. (1:30 PM Jun 26, 2008)
[error] Simulation completed with execution error on server: Local Machine. (1:30 PM Jun 26, 2008)

and :- fault tolerent meshing failed , error in stitch module

i dont know how to rectify it ...can some one suggest something? i will be grateful
Thanx in advance
Rohit Bahl

Can the experienced users of HFSS plz help me.?
Regards Rohit