HFSS Warning Poor convergence in seeding data

Hello,

I am simulating a 2-18 GHz cavity backed spiral antenna in HFSS but I am getting these warnings (mentioned below) in fast sweep when I decrease the spiral arm width to anything below 0.25 mm. I have searched alot on google and HFSS guides but there is nothing on these warnings.
How can i remove this warning message and what do these warnings mean and how do they affect my results?
Thanks

HFSSDesign1 (DrivenModal)
[warning] Fast sweep setup, process hf3d: Poor convergence in computing port dispersion. (5:58:01 PM Dec 09, 2010)
[warning] Fast sweep setup, process hf3d: Poor convergence in seeding data. (5:58:01 PM Dec 09, 2010)
[info] Normal completion of simulation on server: Local Machine. (6:31:33 PM Dec 09, 2010)

I am not an expert on HFSS but may be your mesh is not fine enough when the antenna arm is less than 0.25mm, try using a finer mesh in that area. And another thing that I noticed is that it is complaining about the port dispersion, so may be the point that you are placing the port is too thin. I you cant solve the problem you should post your files here, there are many people who can help you in this forum.

The fast sweep is ideal for relatively narrow-band resonance antennas as it is an extrapolation algorithm about the center frequency. For a broadband antenna, the interpolating sweep is ideal if you only need SYZ. If you require Far Fields, I suggest the discrete sweep. Both of these sweeps will also require less RAM than the fast sweep. Ensure that your solution frequency is the highes frequency in band of interest, ie 18GHz