Ooh that's interesting that some other people are having problems with WP and LJ, makes me feel a bit better that it's not just me.
I use Internet Explorer 7 and always have done so I don't think it's that as such as I've never had any problems with it before.
I use Orange Broadband and have had numerous problems with it over the past year or so, so it wouldn't surprise me if it was them. Hopefully it will fix itself, but hopefully sooner rather than later as I need my blog!