ArgumentError calling Dispatcher.dispatch

Hello. I am hitting a nasty error wherein the the 2nd sequential
request to my rails application is failing with the following error.
Note that I am getting this error with both webrick…

#<ArgumentError: wrong number of arguments (3 for 1)>

…and with Mongrel…

Error calling Dispatcher.dispatch #<ArgumentError: wrong number of
arguments (3
for 1)>

The real pain comes in when looking at the source for both cases,
webrick_server.rb:115 and mongrel/rails.rb:73 and noticing that the
calls do have three arguments.

Any idea how the interpreter would only think one argument is being
passed here?