When a log is defined in Vista for a 24 hour log period no values are logged.
Windows 7 32 bit
There is a known issue with Vista 5.1.6 and time zones of the Vista server PC.
24 Hour logs do not start to collect information if the time zone is set to GMT +2 or greater.
The only resolution currently is to change the log to 12 hourly.
Then use Excel to add these together if this value is used in a Report.
This problem has been fixed in the release of Vista 5.1.6. Upgrading to this version will fix the problem.