Have you tried loading the site with another browser, Google Chrome, Safari, ect...........

Has been working fine for me, no problems.

Welcome aboard Marcel, look forward to your input.

16bit for me also in processing.

Noticed these beautiful orange blooms and although small I thought they would look great with a black background. Shot indoors with side light from patio windows and a black cloth background.



Flames by SFB579 , on Flickr

My K5 has no problems with this lens, SR is fine also.

Really lovely shots there, particularly like the second one.

Many shots to look through there, try posting around 6 or so of what you consider the best for feedback. Never tried Motorsport myself so I can appreciate how difficult it can be to get an original image at racetracks.
A lot seem to be shot from the same position on the track, I suppose your limited as to where you can and cannot go. I would try to pan with a lot more of the shots to try and give an impression of speed. They are nice and sharp and colorful. A lot of good shots there, keep up the good work.

My pick? I'd go with the Tamron 17-50mm f/2.8 XR Di II Lens over the Sigma.