ipad will not charge or reset

I have a third generation iPad that has given me virtually no trouble at all since I purchased it new. During a recent software update the iPad attempted to restart but remained 'stuck' on the 'Apple logo'. I allowed the iPad to sit for quite a while with no change. I eventually plugged it into the charger for several hours (thinking this must be the largest software update in history) but the screen remained 'frozen' displaying the Apple logo. After a while I attempted to reset the iPad and, as expected, the screen went blank with the Apple logo re-appearing in short order...but instead of restarting the screen remained 'frozen' with the Apple logo yet again. When next I tried to reset I was presented with a large battery icon with a small red line indicating (I assume) an almost completely discharged battery. This, despite the iPad having been plugged into the charger for hours. I gave up and left the iPad plugged in for the next 24 hours. The screen is still 'frozen' and the large battery icon still displays as discharged. I have since attempted several different chargers both at home and in the car (the 'event' occurred while I was in a hotel on a business trip). When I got home I tried plugging the iPad into my home computer thinking I could do a complete restore from iTunes but iTunes doesn't even recognize that the iPad has been connected via USB. I have tried using compressed air and a soft brush to clean the iPad pin contacts but nothing seems to make a difference. At the time of the attempted software update the iPad battery was reading about 50%. Any suggestions or insights would be appreciated.