g3nki nice to hear you solved the problem you had... but still continues after 1 day now? it might not bee steam or C2 ... but your hard drive ... is it almost full? what settings you have for caching things? how much space you have in the C2 auto save folder? is it OLD or new ? is it HDD or SSD?
I have a core i5 4670K clocked at 4Ghz with 16GB of DDR3 1866MHz memory, Geforce GTX960 and a Corsair Force LS 240GB SSD. and my other computer is a laptop, quad core AMD A4-5000 APU clocked at 1.5Ghz with built in Radeon 8330 graphics, 16GB of DDR3 1600MHz memory and an unknown 256GB SSD drive. The problem acts out in similar fashion for me. Both computers have 60+ GB free storage.
I simply press Alt + Tab to switch window and then Alt + Tab again to return to Construct 2. This solves the problem instantly for me. I used Construct 2 all day long and could bypass the issue just doing that, but it only happened 2 or 3 times.
I actually was never able to bypass the freezes with alt+tab. Well sometimes Construct semi-freezes for me, but just for a short while, in those cases, alt+tab has worked for me, but once it reeeeeeaaaaally freezes, there's no way to recover responsiveness in the application, the only thing I can do is try to make construct save the changes by pressing the save icon constantly and then try to close the application or force it to close. However, The "disable auto-save workaround" has worked for me.
Nowadays Construct isn't that much of a hassle, especially since I have adopted this workaround.
Enjoy your new "Steam software", I have one more idea that came into my mind today about the sluggishness.
Do you guys have "Mobile Previewing" enabled? (This thing)
Yes and no, on my desktop computer (i5) I preview my creations on a tablet and a phone, while my laptop, which actually have more or less mobile-chip webGL performance I have it set to localhost. that doesn't seem to do any difference to the issue I'm have been having.