On my N900 it happens when I try to manually update the "Other Maemo Weather" applet on the desktop and the only way of stopping it is to reboot the device. Once I've tried an kill hildon-home and it restarted but then all my widgets and applets disappeared, only the shortcuts were left. So now when it happens I simply restart the phone.

I have custom operator name widget installed too but I don't think that it has something to do with it in my case.

It would be good to fix this hildon-home bug, but I don't now if it is fixable.