Paul, it's not you. I'm having the exact same problem with GST, and similar, but not as severe problems, with VirtuaTennis 2009.
For me, GST is pretty much unplayable because the player jitters around and does whatever it wants. Adding the Nunchuck actually makes it worse, because the player won't respond to the joystick control unless it wants to. I.e., I'll hit a cross-court shot, then want to run to the other side to get the return, but he just stands there, or lags several seconds before moving, and I lose the point.
I've tried three different WMP controls, so unless they're all bad, that's not it... plus it seems to work fine on Tiger Woods PGA 10.
Just picked up GST and played it for about a hour online. I really didn't have any trouble controlling or moving my player. Sure it will take a lot more practice to get it down well but that's the cool part of the game, it takes practice to get better. Also remember to hold your WiiMote with the buttons facing up. Personally I think this game is fantastic!!
Okay, so I just rented the stupid NEW EA Sports Grand Slam Tennis game, which of course came without instructions. I popped it in, and LO AND BEHOLD, it auto defaults, just like the f---ing EA Golf games, to a ONE PLAYER practice area. No matter what I try it won't let me move beyond that and sure as hell won't even let me go anywahere else. And of course, I want to reach the multiplayer option.
SO, questions for you gurus out there? HOW IN THE HELL DO I GET TO THE Multiplayer mode? And I am STUCK having to go through the stupid setup practie, what do I need to do to get beyond it???? I already search, so please don't tell me to look for the P1 blue button and move the other wiimote to the right. I DON'T EVEN GET THAT OPTION!!!
I've been at this sh-- for over an hour...HELP, SOMEBODY???!!