The combination I'm trying to make work is Ruby1.9 + Ramaze + Rack? + ?

I'm told there are some issues with Rack, so that might be the problem. 
Mongrel won't install at all (it wants fastthread).

Ebb is the strangest -- it keeps Ruby at 100% CPU, but seems to work (Ramaze 
responds as I'd expect it to.) Thin and Webrick keep Ruby at 3-5% CPU, but 
also seem to work. Keep in mind this is with pretty much the "Hello World" 
Ramaze app, and without any requests -- whatever it is seems to be entirely 
external to the app.

I'm running 1.9.0 (2007-12-25, rev 14709) -- could that be the issue? Is there 
some "hello world" Rack app I could use to make sure it's not a Ramaze issue? 
And is there some combination of framework / webserver / 1.9 version which 
works?

Yes, I know it wouldn't be production ready, and would very likely be entirely 
unstable. This is just an experiment, though; it will never have more than 
ten users.