I'm not sure if I should post this in this topic or in a new topic in the "Bug reports" section, but I'll try posting it here first.
My OS is Windows 7 Home Premium 32-bit, & my version of PDN is 3.5.10 portable. Anyway, on 4-25-2012, I downloaded "Simulate color depth" from here. It works very well mostly, except for this bug. You need to have the "Dither" box checked. Then, if you try to use "Stucki" dithering (which doesn't seem to work at all), it will ignore your attempt to use it, & changing the dithering from "Stucki" to a different dither crashes the plug-in. I'm surprised that nobody has posted this before now (I would've posted about it earlier, but my circumstances kept me away from the internet for a very long time).
Also, the only ditherings that I can find are "Floyd-Steinberg", "Stucki", & "Bayer Ordered 8x8". Any help with that?
Finally, I hope that in a future version, you add color versions of all of the bit modes. I trust that I won't have to try too hard to convince you that the option of keeping your color images colored is as important as making them gray-scaled.