I ran into something similar with Vista once, if I remember correctly it had to do with the "needed allocated" space not being large enough for the "maximum" space to be used correctly, does that make any sense?
Not sure Ted. I had allocated more than 3GBs of shadowstorage. That should suffice for about 5 shadows. On the SSD I did not want to give it too much space. I rely much more on my images anyhow. But sometimes shadows are useful to retrieve a mucked up file.
Anyhow. I resized the shadowstorage with vssadmin and up to now it stays behind the fence. We'll see.
One other factor that will cause shadow copies to use more space is ghosts of old shadow copies, which can be removed in the Device Manager. I don't know that this has anything to do with it going over maximum or not, but a little routine exorcism will keep a tidier house.
I do remember that 3GB is the exact same size I had issues with and when I changed to 4GB the issues ceased, I believe that 3GB doesn't divide correctly as does 4GB in the way storage/sectors are counted.
At 4GB I get between 12 and 14 points; to me almost 2 weeks of System Restore points is plenty; when it's set to auto-create a point once a day.