The skin buffer is used for the parsed skin description, for images and for fonts. The usage shown in the console by the simulator is before loading fonts. On the Clips, each fonts requires 3k in the skin buffer (independent of actual fonts size). The menu font counts, too.
The problem on the Clips is, that the buffer is much too small. On targets with backdrop image support (color targets), the buffer is much bigger (to hold one backdrop image for each screen [menu, wps, radio, etc] but images are shared if the same).
A patch to increase the skin buffer for monochrome targets was sent to the mailing list but seems to not make it into mainline because it decreases the cache for audio prefetching by 12K (from i.e. 6.34MB to 6.33MB).
You can slim down your theme by using the default font (it's free), use smaller/less images or make it shorter (less tokens).