That white screen is from Flash running out of memory I believe.
Are you in a public boss room where there are loads of botters and actual players in the Aeacus rooms farming? Maybe its the amount of animations on screen or something? Try turning off all animations, hiding monsters and dropping graphics quality as low as possible?
You might need to try to manually allocate more RAM, to be honest though I don't know how or if you can off the top of my head. If it's any consolation the same thing happens to me after running Flash for a long time on my machine despite having 32GB of RAM.