After upgrading to the latest OS 4.3.5, I could no longer hear my iPhone hooked up to my Bose soundock. I tried listening to music without headphones and that didn't work either. I could hear everything with headphones but nothing without. I tried using the volume buttons on the side but again there was no sound unless a headphone was plugged into the iPhone.
I remembered having set a volume limit in the Sounds section just short of the full volume. I went back into that setting and adjusted it to the full volume and now everything works!
your hook might only charge because my moms hook only charges and so she uses the back of the speakers to hook it in and it works and your phone might not play music without headphones because some things dont play on there.