Had exactly the same problem occur to my desire S!
Left mine charging and updating a load of apps. Then when i went to check if it had finished updating and i couldn't do anything. It was as good as dead, couldn't get the screen to come on, no charging notification light, nothing. I decided to take the battery out for a reset. After replacing the battery my phone turned on but was stuck booting and it seemed to randomly reload the "HTC, silently brilliant" white screen.
Loading into hboot bootloader i tried to select recovery, but, this brought up a black screen with a picture of a phone and green arrows in a circle then a red exclamation mark in a red triangle where it froze. Then i decided to reset to factory settings via the hboot bootloader. I have reset factory settings before via the main menu to reconfigure the accounts and had no problem in the phone returning to how it was before after resyncing contacts and after it had finished redownloading the apps that were on it before without manually having to go through the marketplace going by memory.
For some reason this time after the factory reset, certain apps which are shipped with the phone such as the camera and mirror applications are no where to be seen in the menu.
The camera can't be accessed via the gallery either.
All my photos are accessible from the sd card, but all the applications i had saved to the sd card just don't show up on the phone for some reason. This is pretty annoying as i can't remember all the apps i had on there, plus they are on there taking up space just not usable. I reset the phone to factory settings without the sd card in there if that makes a difference.
Any help or guidance would be much appreciated, not having use of the camera is my main concern, although the loss of apps is very annoying when i thought the htc marketplace was supposed to remember all the apps you've downloaded and redownload updates...
Thanks a lot
BradJJ