I am trying QtLyx 1.3.0 from Ruurd Reitsma on a win2k machine. The instant preview works after adding the latex preview package to the miktex tree and after adding pnmcrop.exe to the path. However it generates error messages when running sed.exe: something about illegal J command. I think it might be due to the following sed constructs in lyxpreview2bitmap.sh:
sed -e "/${BASE}...etc... here BASE expands into J:\lyx-win32\etc... on this machine. Hence the "command J" (I think that's where it comes from). but despite this problem, the visual appearance of the instant preview seems to be the same as on my linux machine. -- Serge