Hi, I'm having the same problem as Samaha. I'm ending up writing the post, copying it, pressing save - it disappears (apart from the title) and then I paste it in again! 2nd time round it always works fine. I post mainly from work (its a blog for my classes) so its a bit tricky to be specific about security (and I can't change it anyway - no admin rights). But here is what I've got:
Internet explorer - up to date version 6(boo!)
We use 'Fastweb' which is effectively a LAN internet connection (fibre optical wire) - so we can't control the central router anyway, I'd also imagine this means it has a pretty tight firewall. However in my (amateur) opinion its unlikely to be at my end as it has only started quite recently and the school tech hasn't made any significant upgrades or changes to the security settings in the meantime.
I also get the 'loaded but with errors' symbol at the bottom of my browser.
Any help very gratefully received! If there is anything specific that you need to know re: security setting etc please let me know and I'll try to get onto our elusive network manager.