Try resetting nVidia Control Panel's 3D Properties to defaults. If you added PvZ.exe to Program Settings make sure it's all defaulted back too.
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I'm sure you know but no overlay software (RiviaTuner, Fraps, TS overlay, etc). There are some work arounds to make it work with Origin in Game though too.
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Try disabling Origin in Game for a test, just to see.
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Check your processes... perhaps something is eating your CPU up?
Clean Boot even to test
http://support.microsoft.com/kb/929135
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I like playing with this config file... even though we probably shouldn't throw another variable in... here it is:
Open Notepad.
Copy and Paste this:
RenderDevice.ForceRenderAheadLimit 1 ///(You can try changing this form 0 to 3-ish... I think it goes up to 8 but nah)
PerfOverlay.DrawGraph 0
PerfOverlay.DrawFps 1
PostProcess.DofMethod 0
PostProcess.BlurMethod 0
PostProcess.DynamicAOEnable 0
PostProcess.DynamicAOMethod 0
Render.VSyncFlashTestEnable 0
WorldRender.TransparencyShadowmapsEnable 0
WorldRender.MotionBlurEnable 0
WorldRender.MotionForceOn 0
WorldRender.SpotLightShadowmapEnable 0
WorldRender.SpotlightShadowmapResolution 256
WorldRender.LightTileCsPathEnable 0
RenderDevice.Dx11Enable 0
RenderDevice.Dx11Dot1Enable 0
RenderDevice.Dx11Dot1RuntimeEnable 0
RenderDevice.VSyncEnable 0
RenderDevice.TripleBufferingEnable 0
GameTime.MaxVariableFps 60
Save it as "user.cfg"
You cannot have user.cfg.txt
enable "View Extentions of Known File Types" from Folder Options in Control Panel
Put it in your PvZ directory
\\Origin Games\Plants vs Zombies Garden Warfare
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I understand that it's only after the patch... but I don't want to get hung up on that.