[plt-scheme] intermittent "Connection reset by peer" with web server on mac

I worked through the systems programming tutorial again last night, with 
mzscheme 4.0.2 on mac osx leopard, and observed intermittent connection 
failures when making concurrent connections. eg this fails pretty often:

  ab -n 1000 -c 100 http://localhost:8080/

with:

  === context ===
  /Users/simon/src/serve.ss:36:0: handle
  /Users/simon/src/serve.ss:23:12

  regexp-match: expects type <string, byte string, or input port> as 2nd 
  argument, given: #<eof>; other arguments were: #rx"^GET (.+) 
HTTP/[0-9]+\\.[0-9]+"

I see the same thing with plt-web-server, it says:

  output-file: tcp-write: error writing (Broken pipe; errno=32) File a 
PLT bug report if this is on a live server!


Thanks,
-Simon