i also experienced this matter :
1. my S2 got drained within 3-4 hours, this is without turning on my wifi, data, GPS, Bluetooth or simply says i just let it in standby mode ; just for normal usage-texting & make/received call.
2. i've noticed this begin to happened when i'm using external battery charger from Kapersky, when i use it in a while my screen's phone can be 'auto rotate' even i already disable that function & suddenly turn into 'driving mode'.
3. then when i charge with standard samsung charger, it will notified 'MTP Connected" (it still charging, but it just like when i connect the phone to PC via USB)
4. & of course, the phone get hot at the back side.
* model : GT-I9100G on gingerbread 2.3.6
now i already done re-calibrate the battery, lets see how it goes~
before that, thx juo78