Sorry about that 😦
Some “tactical” fools decided to replace the “SSI” file on my site – this file normally creates the right hand column of links, etc and so instead allowed them to temporarily overlay every one of my webpages with some junk graphic.
The original file is back and all seems fine – as far as I can tell, they were able to do this because by default MovableType deliberately creates files with the “world write” attribute turned on! Don’t know why, but it’s annoying.
I’ve turned it off, and asked MT for guidance; meanwhile I’m hoping that (a) it doesn’t cause any other troubles and (b) my site is now safe again.
I suppose I should be flattered that someone thought my site worth targetting! 😉
M&I / GBMINI 
Truly a sign that your site has reached a high level of popularity!
Glad you at least determined the cause, I was worried it was a server issue.
The word “site” triggers moderation on GBMINI.net, which is why your comment didn’t go straight through!
Which files did you have to CHMOD?
The file they hit was my “MT.SSI” server side include, which is pulled in to most of my web pages and creates the right hand column.
But MovableType by default (re)creates it with 666 permissions instead of 644.