Ara, 

>>> http://raa.ruby-lang.org/project/posixlock/ 
>>
>> Just to confirm it compiles fine in Cygwin. Though I don't have an nfs mount available to test with.
>
>   require 'posixlock'
>   def lock_test
>     pid = Process.pid
>     42.times do
>       open(__FILE__,'r+'){|f| f.posixlock(File::LOCK_EX) and puts "locked by <#{ pid }>"}
>     end
>   end
>   fork ? lock_test && Process.wait : lock_test
>
>thanks VERY much for checking that out!!!  i'll start a list of known
>successful compiles - can you give me anymore info?  versions, win platform,
>etc.?

It appears to work see trace below. 

Test run on 

ruby 1.9.0 (2004-08-02) [i386-cygwin]
WinXP Pro
Cygwin Dll version 1.5.10-3

$ ruby ara.rb 
locked by <2212>
locked by <2212>
locked by <2212>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <2212>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <1392>
locked by <1392>
<snip>