Thanks, I've used that method in the past and it looks like I will have to use it again.

It's not just a problem with posting, BTW. It appears that if you do anything that either goes to a different part of the page (i.e. clicking on the "Parent" link) or brings up a new page (i.e. "Reply to This," "Post a Coment," etc.), then try to skip back to the page you were reading using the back button on your browser (usually Alt-Left Arrow, but you can also skip back multiple pages via the drop-down back menu), then you lose all your "[new]" tags. I think somewhere along the line the page is being forced to reload, which blows away the old "[new]" tags and brings in the next set.

This is a recent change in behavior, and I can't figure out whether it's in my browser (Mozilla Firefox 2.0) or a recent change in the Oil Drum web site.

I think it's your browser, because "back" still works for me (in Firefox 2 and 1.5).  

You might trying emptying your cache and/or increasing its size.