Its funny that you dont take the time to provide a direct link instead of saying "Go here, they might have it" But I will:
Download Plus! 3.25
And instead of downgrading, why dont you disable some of the custom sound feature and see if that helps?
Plus! -> Preferences -> General Options -> Sounds -> Then untick the 3 options under "Custom Emotion Sounds"
And if you want to remoce the speaker and the Plus! logo in conversations go:
Plus! -> Preferences -> Instant Messages -> Untick "Enhance the toolbars with Messenger Plus! features"
First do what I said, and if that doesnt help, then you can downgrade
/ 
