I do lots of these panos, same files, formats. on this one, one of the created files ends up 8 bit while the rest are 16. The original files are all 16 bit tif.
This was repeatable - but I had run 6 or 7 panos without restarting hugin - so after it failed twice, I quit, restarted and tried stitching the same PTO - and it made no difference.
Version is 2010.1.0 SVN5156 built by Harry van der Wolf
Checking nona...[OK]
Checking enblend...[OK]
Checking enfuse...[OK]
Checking hugin_hdrmerge...[OK]
Checking exiftool...[OK]
/Applications/Hugin2010.1.0/Hugin.app/Contents/Resources/HuginStitchProject.app/Contents/MacOS/nona -z PACKBITS -r ldr -m TIFF_m -o OH4 -i 0 /var/folders/Ct/Ct8wFiyWE10+pvl1juUg4U+++TI/-Tmp-/huginpto_IbjGSG
/Applications/Hugin2010.1.0/Hugin.app/Contents/Resources/HuginStitchProject.app/Contents/MacOS/nona -z PACKBITS -r ldr -m TIFF_m -o OH4 -i 1 /var/folders/Ct/Ct8wFiyWE10+pvl1juUg4U+++TI/-Tmp-/huginpto_IbjGSG
/Applications/Hugin2010.1.0/Hugin.app/Contents/Resources/HuginStitchProject.app/Contents/MacOS/nona -z PACKBITS -r ldr -m TIFF_m -o OH4 -i 2 /var/folders/Ct/Ct8wFiyWE10+pvl1juUg4U+++TI/-Tmp-/huginpto_IbjGSG
/Applications/Hugin2010.1.0/Hugin.app/Contents/Resources/HuginStitchProject.app/Contents/MacOS/nona -z PACKBITS -r ldr -m TIFF_m -o OH4 -i 3 /var/folders/Ct/Ct8wFiyWE10+pvl1juUg4U+++TI/-Tmp-/huginpto_IbjGSG
/Applications/Hugin2010.1.0/Hugin.app/Contents/Resources/HuginStitchProject.app/Contents/MacOS/nona -z PACKBITS -r ldr -m TIFF_m -o OH4 -i 4 /var/folders/Ct/Ct8wFiyWE10+pvl1juUg4U+++TI/-Tmp-/huginpto_IbjGSG
/Applications/Hugin2010.1.0/Hugin.app/Contents/Resources/HuginStitchProject.app/Contents/MacOS/nona -z PACKBITS -r ldr -m TIFF_m -o OH4 -i 5 /var/folders/Ct/Ct8wFiyWE10+pvl1juUg4U+++TI/-Tmp-/huginpto_IbjGSG
/Applications/Hugin2010.1.0/Hugin.app/Contents/Resources/HuginStitchProject.app/Contents/MacOS/nona -z PACKBITS -r ldr -m TIFF_m -o OH4 -i 6 /var/folders/Ct/Ct8wFiyWE10+pvl1juUg4U+++TI/-Tmp-/huginpto_IbjGSG
/Applications/Hugin2010.1.0/Hugin.app/Contents/Resources/HuginStitchProject.app/Contents/MacOS/nona -z PACKBITS -r ldr -m TIFF_m -o OH4 -i 7 /var/folders/Ct/Ct8wFiyWE10+pvl1juUg4U+++TI/-Tmp-/huginpto_IbjGSG
/Applications/Hugin2010.1.0/Hugin.app/Contents/Resources/HuginStitchProject.app/Contents/MacOS/enblend --compression NONE -l 29 --fine-mask -w -f12688x1551 -o OH4.tif OH40000.tif OH40001.tif OH40002.tif OH40003.tif OH40004.tif OH40005.tif OH40006.tif OH40007.tif
enblend: input image "OH40007.tif" has pixel type UINT8,
enblend: but previous images have pixel type UINT16
gnumake: *** [OH4.tif] Error 1
The file OH4.pto was added: None