DEPRECATED_INSTANCE_VARIABLES error deploying frozen edge app

My frozen edge app won't run in production (ruby 1.8.5, typical apache
-> mongrel_cluster)

In mongrel.log, I get an error reporting an unitialized constant

so Rails doesn't even start up. Works fine in development (Mac OSX).

After a fair amount of googling, most people install libopenssl-
ruby1.8, and that fixes it but they don't know why. However, I'm not
using any SSL features in my app. Maybe edge rails needs it anyway?

Anyone else have this problem?