The sites in question are Web Dev News and Attackr.
I upgraded to v0.9, and now cached pages don't seem to be getting served. I can clear the cache and wp-content/cache/supercache/*site* gets emptied. Then I can visit pages and I get things like wp-content/cache/supercache/webdevnews.net/about/index.html but every time I reload that page I get a new timestamp at the bottom (bold part changes for every load):
<!-- Dynamic Page Served (once) in 0.829 seconds -->
<!-- Cached page generated by WP-Super-Cache on 2009-01-28 08:13:02 -->
I almost forgot to mention. I saw the the mod_rewrite rules had changed some, so I copied the old rules over and it didn't fix the problem. The plugin added the WP_CACHE constant to my wp-config.php (first non-comment line inside the php tags).
If you need any additional information or want me to try something, please feel free to ask. I'll check here regularly, or you can E-Mail me wpforum@xavisys.com. I can also get you access to the blog and or FTP if it would help.
Just so everyone knows, this seems to be a problem with my host (http://www.mosso.com). They're working on it.