Anna, yoou're using a virtual HD? Did you created it with IMGtool? To make a floppy img/dsk what program trhat you used? IMGtool again? Thank you!
The harddisk emulation for any PC or compatible driver is broken, since the dma devices was fixed in version 0.133 Judge maybe will fix it. I use a external tool called WinImage to create or edit PC disk images. For the chd images, I use chdman.