This is a well-known issue, I've yet to read anything that will definitively fix it.
Here's what
tbohman posted in another thread:
"there is a fix and after lots of trial and error I found it you need to go into control panel admin services then component services then services local click x10 device networking then stop the service then you can open vanguard and record again each time you stop recording you might have to stop the service again but it will record for as many days as you want as long as you dont stop the recording if you do you will have to stop the service before you start to record again"
That's hardly what I'd call a fix - but hey, thanks for playing...
We - and X10 - need to face facts here.
Vangaurd Internet Control Centre DOES NOT WORK as advertised for most people, and the vendors have shown
no interest in correcting a known problem.
Of course, this is just my opinion - and that of many of the other posters in this thread. But who knows? It might just work for someone. They should buy lottery tickets...