James, I know you've probably read replies like this dozens of times and I know it's easy for someone with a decent meter to say it's not a WGT fault but, did you have anything else running at the same time? Other browser windows open or processes running in the background?
When I play a game I only have the game client open, nothing else. I also use Maxthon to play in and for nothing else so I know it isn't full of junk. I used to use Game Booster but haven't for ages now and it's not even installed on the new computer. I have a pretty slow internet connection by today's standards but this shouldn't make any difference anyway as the meter movement takes place without any input from WGT.
I have a very occasional meter fluctuation but it's been well over a year since I had a really big one that caused a disaster shot.
Given how tiny the moving meter is it really shouldn't come down to how fast your computer is, a 286 should be able to move that smoothly. I often wonder if certain releases of Flash have issues with WGT, that's one of the reasons I'm still using 11 something to play.
I know it's not what you want to hear but it probably is an issue your end. A week or so ago I disconencted my network cable when standing on the tee and it wasn't until after I'd clicked to hit the ball that the game froze. That means the meter's movement takes place entirely within your computer, it has to be something there causing the problem.
Could you check which Flash version you're using? And let us know which Browser you're using to play?
There has to be a way to get a decent meter without putting in too much work, I only do very basic stuff and have very few problems.