Just a quick update, Alexey. I also tried this on an early 2013 iMac (10.8.5) and it had the same issue. I also tried disabling all extensions (Safe Boot mode) and the problem was still there. I also tried it in 10.8.3 and it was the same (works in 1760, broken in 1771).
Once again, it's only with Mosaic and Average texture builds, it still works if I use Max or Min intensity.
Please let me know if there is anything else you would like me to try, or even if you would like me to run a special debug version, etc.
Cheers, -C