Can't post here either (Opera 11 Windows 7.)
I suspect it may be a javascript problem:
About 3-5 weeks ago I lost the ability to preview, and noticed the "preview" button was a smaller font to the "post" button.
Now both the buttons have a smaller font (when clicked), and neither work.
I had (and still have) switched javascript off in my browser (for MN only) because it appeared that in order to fix a "save .js file ?" type dialog popping up sporadically you had changed from executing javascript internally to externally.
This was causing all MN pages to hang; presumably waiting for the JS to execute externally.
Simply turning off javascript worked.
Except now, the javascript controlling the post/preview buttons has been changed and now won't work without js enabled.
Sorry to be blunt but I feel this may be a case of if it isn't really broke don't fix it; the "save .js file" thing, whilst anomalous, really wasn't causing any ultimate problem. (Or did you think this was a likely cause of server slow-down ?)
It's not clear what "problem" the post/preview buttons were causing.
Seriously they were fine as they were.
And now there is a problem.