When you say "0.7.27 with Qt library" do you mean the version linked to in
this thread? That's a beta version and may (or may not
) have multiple issues. Also, is your computer reasonably powerful? What version of Windows (I'm assuming you're running windows since you mentioned the disk space check taking a lot of time, which is a known issue) are you running?
The disk space check on install takes quite a bit of time, I've had instances of it running without updating the screen for several minutes. Search the forum if you're interested in the reasons. The slow calibre response might, if you have a somewhat older computer, be entirely normal, although it sounds a bit excessive. If you downloaded the normal version (from
here), I'd suggest waiting for the next release, due out sometime at the end of the week, I believe, which should bring a quite noticeable speedup due to a new version of the Qt library. If you already downloaded the beta version from the thread I linked to above, try asking inside that thread for help or wait until the version is officially released.