Well, it seems there is no solution, but i have the same pb with the last since the beta R123 :/
Everything works well if i go back to R122.
If it continues, i will reformat my pc, cause i tried everything.
But I notice that all the other softwares work well (photshop, cubase and co), and I have only that pb with Construct2.
I'm on Win7 64 bits pro, on a dell laptop.