Sometimes the UFRaw-rendered image looks like it has blown pixels when the raw file for sure has no blown pixels. Using dcraw -H 0 -W -o 0 with an appropriate -S value, then assigning the same camera profile used in UFRaw gives a smooth histogram, no blown pixels. Additional negative exp. comp in UFRaw just moves the spike down. Changing the white balance does eliminate the spike in one channel but can move it to another channel. See http://www.dustystones.com/2010/photo-essays/ufraw-highlights/ufraw-highlights.html for more details and sample files for download.
New link to details ans sample files: http://ninedegreesbelow.com/bug-reports/ufraw-highlights.html
Regards,
Niels Kristian