Forum Style reversing willy-nilly?

[محروم.كوم]

I'm having a small problem with the style of my forum:
I've customized my own style and made it the default one. However, every now and then it reverts back to the original. For example when posting new articles in the CMS or sometimes when you use an alias for the domain. So I'm just wondering if this is some kind of bug or if I've just missed some setting?
Oh, and is there a way to not even make the original style viewable to the users? I thought I'd removed it from the list, but it's hanging in there like a bad habit.

Thanks in advance for any assistance! __DEFINE_LIKE_SHARE__