sqiddster Yeah! I looked into it and found a workaround though yesterday. <img src="smileys/smiley16.gif" border="0" align="middle" />
I think when you open an event sheet or "Loose focus on an event sheet thats opened, like when adding an action, then returning focus", it will load each layout that has the eventsheet loaded (for reasons I'm not sure). I'm guessing you also have lots layouts with lots of layers and lots of sprites placed around, so when you even click a single layout thats not loaded, it will take 1 second to load.
Now; since the event sheet is loaded for each layout, that means every layout that has the event sheet will cause an extra +1 seconds of waiting time when you focus on the EventSheet. For me, it comes to about 5 seconds (It seems faster the less time Construct 2 has been open)
SO THE IDEA IS, have an eventsheet that literally just contains an "include" sheet to your MAIN eventsheet that was originally on all tha layouts, then on each layout, make sure it loads this new eventsheet.
After doing this, It removed ALL the lag from clicking onto the eventsheet that I use, and the "Include" eventsheet lags instead (but you'll never need to click it, so hooray <img src="smileys/smiley4.gif" border="0" align="middle" />)