symdns and symredrv drivers keep disappearing!

I fist noticed this last week or so when I ran a diagnosic app that showed 'file not found' for symdns.sys and symredrv.sys.

Rebooting didnt help. I also notice my nighly scheduled scan of my boot drive wasn't happening tho I can still run it manually.

Norton scan comes up clean, OneCare online comes up clean.

So I reinstall NIS 2009 and the drivers reappear and the the 'all clear' screen from the overnight boot drive scan greets me every morning once again. 

Now about a week later, the same drivers have disappeared and my scheduled boot drive scans are not happening...btw the xp scheduling service is on.

The scary thing is I get no errors or crashes as a result.

 

Does anyone know what is going on?? Thx...Mm