Clipping paths on 64bit architecture

Hi, I'm converting CMYK tiffs to PNGs and using the embedded clipping  
path in the TIFF to create transparency in the PNGs.

I'm using the command:

convert test.tif -profile srgb.icc -colorspace rgb -fill white -draw  
"color 0 0 reset" -transparent white -clip -draw "Image Copy 0,0 0,0  
test.tif" -geometry 200x200 test.png

It works great on 32bit machines (Linux or FreeBSD), but it fails  
strangely on any 64bit machine I've tried it on.

You can find some example files, named by the platform, IM version and  
if it's broken or not, here:

http://nevada.net.nz/~pmurray/imagemagick/

Is this a known bug? Has it been fixed in a later version (I couldn't  
find any reference in the ChangeLogs) ?

Thanks!

Phil