I have seen this as well in the Application and Device Control log. To reproduce the behavior:
1. Open up the A&DC log.
2. You will see both the date and time in the Time field.
3. Wait for the log to refresh.
4. Only the time is now displayed in the Time field.
SEP RU 5 client and server. Server runnign on Server 2003R2. Clients on Windows 7 RTM.