Theme not working?

[Sogarth]

I've been having a really strange problem - if I try and change the theme on my Today screen, nothing happens. As in, I can put another .tsk file in \Windows, and try and select it from Settings -> Personal -> Today... but it keeps showing the Windows Default theme. Now, it could entirely be due to some of the ROM work I've been doing, but I can't imagine what I did that's caused this. Has anybody else encountered anything like this, and even better, does anybody have any clue how to fix this? Thanks!