I host the site with Dreamhost. Everything is OK for almost two years, until last month. I met so many internal errors when I login, publish or rebuild. Sometimes I just click the link in the back.
The error.log has something like below:
[Tue Dec 02 14:50:54 2008] [error] [client 64.180.100.153] Premature end of script headers: mt.cgi, referer: http://www.yinfor.com/mtcgi/mt.cgi [Tue Dec 02 14:50:54 2008] [error] [client 64.180.100.153] script ‘/home/davidyin/yinfor.com/internal_error.html’ not found or unable to stat, referer: http://www.yinfor.com/mtcgi/mt.cgi
Any one has similar problems?
Reported on Movable Type 4.2

Does this happen randomly, or does it happen mainly on certain things?
It happens very often during last 20 days.
I can not publish any post now.
And you didn't recently install any new plugins or updates that would affect the code?
No new plugins installed.
Based on the hosting support's answer, it is because of the cpu / memory usage is over the limit. Then it is killed.
How to reduce the memory or cpu cost?
I use fastcgi already.
Well... you can make heavy use of template module caching to reduce the amount of time that a rebuild takes, but this is more of an issue with your host being cheap. I had similar problems when I used Dreamhost. They compete with others by overselling their resources.
DavidYin, you should also look into using PubilshingQueue for the templates that are most problematic. Unlike web-based requests, PublishingQueue processes (which are executed by cronjob) are usually left alone by hosting providers.
You may also want to invest some time into profiling your templates to figure out which ones are problematic. Pages like Google Sitemaps and any published using the Paginate plugin are common causes for timeouts (or process reaping by overinvasive hosting providers) during rebuilds.