While in Virtualmin, I go to Configure Apache Modules in order to enable headers and expires. When I click Enable Selected Modules, I get this:



My Apache server shut down by itself. I restarted it and now I notice that headers and expires seem to be enabled, which is good, but I'm unsure as to how that error message may affect my system.

How do I fix this?

Ubuntu 8.04 LTS
Virtualmin 3.76
Apache v2.2.8

It sounds like you tried to start Apache when another Apache instance was already running. Don't know why Virtualmin would do that, but it's probably not an ongoing problem if Apache now runs with the new config.