Please attach the extracted dc42 file and perhaps a clue will appear...
From .zip Attached.
The un-zip' and un-sit' match, so I surmise your downloads are working fine.
The issue appears to be that at some point FloppyEMU stopped recognizing sparse DC42 files as being valid. The documentation implies they should be recognized so I expect this is an oversight and since sparse files are very rare I suppose no-one has reported it.
I've uploaded a non-sparse DC42 that works (for me) with the recent version of femu... item (W) of
http://www.sigmasevensystems.com/blu.htmlUnzip and copy "BLU090_400k.dc42" to your FEMU memory card.