Answering my own questions...
Bruce,
Here's a fix for you. Even though I'm not using the performance control template, the performance is still being calculated - That's fine
In NetWebServer._PerfEndThread you have this line -
self.PerformanceLoad.RequestsPerMinute[(clock()%360000)/6000,clock()/360000,day(today()),month(today())] += 1
That causes the error -
Every hour, for 1 minute, clock()%360000)/6000 = 0
Everyday, for 1 hour at midnight, clock()/360000 = 0
This should fix it -
self.PerformanceLoad.RequestsPerMinute[(int(clock()%360000)/6000)+1,int(clock()/360000)+1,day(today()),month(today())] += 1
Now I'm going to try the performance control thingy.
Chris