Way too many 500 Internal Server Errors on GoDaddy

I have a multi-site install hosted on GoDaddy, still in the development stage, still only a handful of posts on four different blogs. When I started working on the sites, I noticed that page loading was usually very slow. Then I started getting 500 internal server errors from time to time, and very, very, very slow page loads. Today, I have changed nothing from yesterday but have had more 500 errors (and a few access denied errors) than successful page loads (both admin and blog pages). It is all intermittent — sometimes a page will load, sometimes the same page won’t load — so I assume the problem is with GoDaddy, not my sites. (My sites use Suffusion for the theme, and a handful of standard, widely recommended plugins.) Early on I asked GoDaddy about this problem and they supposedly checked their servers and said everything was OK on their side, it had to be my site — but I’m not sure I buy that.

Here’s a sample of what my error log reports:

[Tue Jan 4 16:58:34 2011] [error] [client 24.6.251.212] FastCGI: comm with (dynamic) server “/var/chroot/home/content/r/c/e/rceckhardt/html-x-httpd-php5” aborted: (first read) idle timeout (60 sec)
[Tue Jan 4 16:58:34 2011] [error] [client 24.6.251.212] FastCGI: incomplete headers (0 bytes) received from server “/var/chroot/home/content/r/c/e/rceckhardt/html-x-httpd-php5”
[Tue Jan 4 17:02:35 2011] [error] [client 24.6.251.212] FastCGI: invalid (dynamic) server “/var/chroot/home/content/r/c/e/rceckhardt/html-x-httpd-php5”: script not found or unable to stat()
[Tue Jan 4 17:03:36 2011] [error] [client 24.6.251.212] FastCGI: comm with (dynamic) server “/var/chroot/home/content/r/c/e/rceckhardt/html-x-httpd-php5” aborted: (first read) idle timeout (60 sec)
[Tue Jan 4 17:03:36 2011] [error] [client 24.6.251.212] FastCGI: incomplete headers (0 bytes) received from server “/var/chroot/home/content/r/c/e/rceckhardt/html-x-httpd-php5”

Does anyone know what causes these errors? Is there a clue in here as to something I need to fix? Thanks.