I just tri with defaut scene when DazStudio open

And i have access to reality interface

My version :Reality version 2.5 -- Build: 2.50.1.122

Here what i did :i load a scene  saved before,remove all the lights and put one of the light prop coming with Reality (here sun light because it a beach scene but i meet the same problem with other prop lights)  after position the prop i click Render Reality 

Sometime it works and i have acces to Reality interface sometime it just pop up and return to DAzStudio   

Here the last lines of the log from one try with popup without acces

DEBUG: 0: Toolkit found: D:/DAZStudio4 64 bits/scripts/Reality/RealityToolkit.dse
DEBUG: 1: Toolkit included
WARNING: Unhandled error while executing DAZ Script.
DEBUG: 0: Toolkit found: D:/DAZStudio4 64 bits/scripts/Reality/RealityToolkit.dse
DEBUG: 1: Toolkit included
DEBUG: 2: Reality Toolkit v.2.0
DEBUG: 3: UI created in 0.414 seconds.
DEBUG: 4: Shutting down the material preview task...
DEBUG: 5: Done.
DEBUG: 0: Toolkit found: D:/DAZStudio4 64 bits/scripts/Reality/RealityToolkit.dse
DEBUG: 1: Toolkit included
WARNING: Unhandled error while executing DAZ Script.

the worst problem is the one like this ,intermittent

For info my system is Windows 8 64 bits,Intel i7 ,32 gigs ram, GtX660 video card,Intel SSD 240 gigs and two hard disk (1 terta and 2 tetra)