The only light in the sun (150%)

Sky outside is a dome but not visible in raytracing and no light emitter.

I checked all the materials in the room, but I did not find anything strange.

Do you recommend?

Thank you.

Try increasing the indirect light quality.

IIRC, by switching off Irradiance Cache (for IDL), you can avoid these splotches. But it tremendously will increase render times.

I haven't read anything that this got better with PP2014 tho.

Done, the same shadow problem.

Yeah, BB suggested switching off IC to eliminate those artifacts... See this thread.

http://www.renderosity.com/mod/forumpro/showthread.php?message_id=4061429&ebot_calc_page#message_4061429

i have made this test this mornig primorge, but render time is very very very long....

and the room is empty....

Your pixel sampling seems rather high.

Yje image is lit by tqo panels with an ambient value of 10.

The artifact is not evident o the red cube but it does show a little on the plane it's resting on, not so much as with the cube that is the same colour as the floor though

You can still see them at the far wall where it meets the floor.  But better.

Does look better... hborre is right also about your pixel samples. I'd say samples of 8 is the highest range for quality that I would go, many would think that 8 is too high. That's definitely contributing to the render time.