iPhone battery drain and crash at 50

My iPhone 4, since updating to the most recent software, had started crashing when it gets down to 50% and 50% on the dot everytime. Now it seems to crash whenever it feels like it but never will it get below 50%. The only way the phone turns back on is when it is connected to a power source once again. I don't even get the dead battery signal when trying to re-boot or anything. Now it would sound like the issue is my battery but I booted up my 3GS with the latest update and same exact thing happens which leads me to believe it's Apple and their ever-so-terrible software.(have they ever released software that left phones in perfect working condition??NO) So maybe its my back-up right? I restored and set up as a new iPhone, same problems. The battery drains from 100%-90% @ regular speed and from 90%-70% the thing reeeallllyyy starts moving quick and from 70%-50% it's just a guess as to when it will die in that region. The issue is such a deal that it's basically renderring my phone useless. If I wanted to leave a phone plugged into my wall I would still have a house phone. The Idiot bar employees told me that the software showed no glitches but that was only dated back to my last restore which was just hours before entering the store. The idiot bar employee also told me that the battery drain issue was "not a known issue" for iOS5. ARE YOU KIDDING ME!? It's all over the internet! So far in my searching I have found few people with my crashing at 50% problem but I have found NO solution. Ya got any ideas?