binavik,
Being the author of the theme...I certainly can help you with this

Did you follow the note in the theme's description that mentions that you need to be running a current build?
As in: Not a "release" build (3.5/3.5.1 etc.)
Current builds for the Nano are located here:
iPod Nano 1st GeniPod Nano 2nd GenThe problem is (I think) that there are at least two features that this theme uses that the current release does not include, this theme likely won't work with "release" builds until 3.6 is released.
I hope this helps you, please, check back here if this does not work for you, though I am almost positive that updating your build will fix this problem.
Thanks for your interest in the Symmetry theme,
[St.]