I use the VH but maybe not as extensively as you.
As I am about to get more deeply into VH options I am keen to see if I have the same problems.
The trouble with intermittent problems is that they are usually extremely hard to fix (if not, impossible) - you know the analogy - it's that classic "occasionally the car won't start" - the mechanic has a massive task in order to find the problem.
So, if I find anything I'll get back here and see if we can't get some sort of pattern as to what is happening.
Cheers
Pete
