After I updated to WordPress 2.3.3, I was seeing some pages in my admin screens getting errors like this:
Allowed memory size of 8388608 bytes exhausted
WTF? So, pages still worked though. I cleaned out everything I wasn’t using (themes, plugins, etc) in my WordPress directories, still getting it.
So researched a little, had to edit my php.ini in the etc directory of my webhost. I changed memory_limit from 8M to 16M. Pages started working again. cool!
Anyways, Windows Live Writer was getting an error on posting after I upgraded "Invalid response document returned from XmlRpc server" and the post would save as a draft in WLW (but still post to my blog) After posting to the WLW groups on MSN, Joe Cheng at Microsoft wrote me to send me the WLW log file. (Help->About->Show Log File). After looking at the log file myself I noticed the same "Allow memory size…" errors and realized that the php.ini fix probably fixed the posting problem.
After I fixed the php.ini, my posts now go through with no issue.
I know some people have just updated the xml-rpc.php and they are having issues. I recommend just updating your whole WordPress installation. If you are using a custom theme you are ok. Just disable your plugins and re-enable after updating the files. the wp-config.php doesn’t get overwritten, so you are ok.
Steve Novoselac's Blog 