Do you have any specs re your hosting environment? i'd check fundamentals (cpu, ram, disk, other customers on the same box) before installing more modules.
This is not good: :-(
http://codesorcery.net/2007/07/23/boost-your-drupal-site
"The second issue is that currently, Boost will not work for sites that are not at the top-level. That is, if your site is domain.com/mysite, it will not work -- only domain.com would work."
This is bad for me because my Drupal site is not top-level.
Daniel.