Just to expand, after two minutes I get this:
PHP Fatal error: Maximum execution time of 120 seconds exceeded in C:\aWeb\bellaforums\libs\ubbthreads.inc.php on line 888
but there's nothing showing up in my UBB error log nor in a PHP error log. Which seems odd to me. And there's no entry in the MySQL slow query log for this. Other things do occasionally write to the slow query log so it's working.
The post does get made. The sidebar does get updated. But the RSS feed doesn't get updated. I'm trying to figure out how to step through the code to figure out where it's jamming. It's been a long while since I've had to be in the internals of the code like this.