freeradius2.1.6| buffered-sql | acctstoptime problems

Hi All, I'm using freeradius2.1.6 with buffered-sql , detail files for accounting. In accounting queries i observed acctstoptime = %S. my db some how freezed and radius stopped updating packets from detail.wotk file. When restarted it started updating but updating the packets with new timestamps instead of old timestmaps whatever in detail.work file. How to overcome this? please suggest. Thanks, Rams.