If this is what i think it is... then i may have a workaround.
i think it's linked to when playmaker is open on the screen... so, if i'm testing a rather hefty game system and have the editor window open, it slows down (since unity has to handle running the game AND running the PM windows.)
one way that i've managed to do a workaround is to put non-playmaker tabs in the windows... so, for the editor i have the native console as well... if it slows down, i switch it to that and that frees up some speed. same with globals... put the particle-effect window on that. i also have the action list share the same space with the inspector (this also helps when i'm testing variables becaus ei can tell them to be visible in the inspector so that i can see what's going on.)
not 100% sure this is what you're facing though... so, if you know your computer's system specs, that could help point you/us in the right direction.