I've noticed lately on my Windows 7 x64 PC that Inkscape (v0.48.4) is very slow to startup. Once the window becomes visible it will display "Not responding" in the title bar for a minute or two. Once it gets out of this fit it runs normally and smoothly.
I tried deleting the Inkscape user profile (
%APPDATA%\Inkscape) and that helped for a while. But the problem just appeared again within a week.