CorelDRAW X5 :: Slow Screen Update With Thick Pen Objects?

I have 2000 objects in my drawing and they all have outline pen widths that are abnormally thick, say 5000 mm. I'm using that method to export additional info with the AI file. Of course, I use Simple Wireframe view model. 

Whenever I change an object, X5 takes about 90% CPU for about 8 seconds,and during that time I can't do anything else with Corel Draw.

I suppose it is drawing somewhere and thick lines take too much time.If I change all the objects to Hairline, or I enable Manual refresh, things work smoothly.

Is there anything I could do to prevent X5 from drawing all objects somewhere? I've tried disabling Use Off-screen image, but that doesn't work.

I thought it was Windows Aero, creating taskbar thumbnails, but I suppose that happens only when the thumbnail is actually visible on-screen.

BTW, Corel 11 and Corel 7 don't care about pen thickness...