Really? different headphone jacks are different sizes? could you link to another website which confirms the adaptor you use? just a standard headphone extension I'd imagine. as every other headphone , aux lead or mic I've used fits, and works in any socket?
The HTCs seem to have sporadic prblems with its headphone jacks.
My girls phone won't hook up to her new sound system, but mine will...surely thats her phone which is out oforder....
<edit> Just solved the problem..sort of....tried every aux cable in the house...it worked only with the chubbie one my mate uses for his cd decks....
Headphones (even the htc) stick out 1mm but work fine, but aux cables...apart from the one I just pinched...do't work at all.
conclusion htc has expensive tastes for speakers out...hope that means the sound quality is something special.....