[plt-scheme] Require intermittently working

I am trying to use the socket library from planet, and am getting
weird symptoms. Sometimes when I require it with the line:
(require (planet vyzo/socket:3:2))
, it works and other times I get error messages of the form:

/Users/eric/Library/PLT
Scheme/planet/300/4.2.5/cache/vyzo/socket.plt/3/2/main.ss:24:13:
except-in: identifier `socket-accept' not included in nested require
spec at: "_socket.ss" in: (except-in "_socket.ss" socket-accept
socket-connect socket-recv socket-recvfrom socket-send socket-sendto
socket-sendmsg socket-recvmsg)

 === context ===
/Applications/PLT Scheme v4.2.5/collects/scheme/private/reqprov.ss:398:5
try-next
try-next
/Applications/PLT Scheme v4.2.5/collects/scheme/private/reqprov.ss:203:2
/Applications/PLT Scheme v4.2.5/collects/scheme/private/modbeg.ss:46:4
standard-module-name-resolver

Normally if I get the error message it fails to run correctly. But If
it is the first time I download it from planet, it gives error
messages prefixed by "setup-plt:", but works. I am also able to get it
to work from DrScheme if I run the program a second time or create a
second REPL (by running the blank program a second time), but not if I
require it a second time in the original REPL.

I am running OS X 10.6.3, and tried multiple versions of plt-scheme
including 4.2.4 and 4.2.5. I have the same problems on 10.5.8, but no
problems with Linux.

-Eric