Performance Problems on Virtualmin GPL Debian Etch AMI

I've installed your Virtualmin GPL AMI and added a couple of packages to satisfy requirements for Magento. On an m1.small instance performance is not overwhelming (much better on m1.large instance), but what still bothers me is the results of ApacheBench.

Calling a static HTML file with ApacheBench has the following fast results:

http://pastebin.com/m2db1d962

But calling a Magento product detail page (or any other page of the store) results in 98 out of 100 requests to fail:

http://pastebin.com/m39666de3

Apache Error log is empty, access log looks like this:

http://pastebin.com/m749ea353

apache2.conf (default config, only error level changed from warn to debug):

http://pastebin.com/m2bcdcfe8

I have no idea why performance is to poor, so any pointers as to what might help to improve on performance would be very much appreciated.