Xperia X10 :: Battery Drain While Remove And Replace Back?

I face one problem today is that for cleaning my X10 i shutdown my phone and i remove the battery, on that time the battery is upto 85% charge .after a couple of second i reinsert the battery and reboot my phone. while rebooting it shows that please connect the charger the battery is low and it automatically shutdown. this is first time i am seeing likeproblem or ?. But all the phone if we remove the battery and reinsert ther is a little % will be discharged.