inserting subfigures in lyx 1.6?

[Micha]

How do I insert subfigures in lyx 1.6?

I tried inserting another figure in the figure, it shows up as a subfloat:
figure with a caption Sub-Figure a: but when I try to compile the document I
get the error:

no counter [EMAIL PROTECTED]

 \subfloat
               []{
Your command was ignored.
Type  I <command> <return>  to replace it with another command,
or  <return>  to continue without it.