Emulator

What's the problem?
When playing Wii Sports' Tennis in split-screen the FPSes drop down. In single player I have 60 FPS (Framelit 60) but when i go multiplayer i have 30-35 FPS.

Dolphin version with the problem (as it appears in the title bar, Ex.: "R
4779" or "R 6403M"):
R 6728

Operating system and version:
32-bit or 64-bit:
Win 7 Ultimate x64

Game ID (as it appears in game properties, Ex.: "GZ2P01" or "RSBE01"):
RSPP01 (I'm using the PAL version]

Was the ISO a plain dump from disc, compressed and/or scrubbed?
Plain dump

Please provide any additional information below.
PC Model: Acer Aspire G7700
CPU: Intel(R) Core(TM)2 Quad CPU Q9450 @ 2.66GHz
RAM: 2x2GB DDR2
GPU: 1xNVIDIA GeForce 9800 GTX/9800 GTX+ with latest drivers