dlopen error 128 with createlang

I tried to install languages into PostgreSQL 7.4.3-1 and ran into the
following problem:

$ createlang --echo plperlu test
SELECT oid FROM pg_language WHERE lanname = 'plperlu';
SELECT oid FROM pg_proc WHERE proname = 'plperl_call_handler' AND prorettype =
(SELECT oid FROM pg_type WHERE typname = 'language_handler') AND pronargs = 0;
CREATE FUNCTION "plperl_call_handler" () RETURNS language_handler
AS '$libdir/pl
perl' LANGUAGE C;
CREATE LANGUAGE "plperlu" HANDLER "plperl_call_handler";
ERROR: could not load library "/usr/lib/postgresql/plperl.dll": dlopen: Win32
error 126
createlang: language installation failed: ERROR: could not load
library "/usr/lib/postgresql/plperl.dll": dlopen: Win32 error 126

By checking plperl.dll, I noticed that cygperl5_8_2.dll was missing:
$ cygcheck /usr/lib/postgresql/plperl.dll
C:/cygwin/lib/postgresql/plperl.dll
C:\cygwin\bin\postgres.exe
C:\cygwin\bin\cygcrypt-0.dll
C:\cygwin\bin\cygwin1.dll
C:\WINDOWS\System32\ADVAPI32.DLL
C:\WINDOWS\System32\ntdll.dll
C:\WINDOWS\System32\KERNEL32.dll
C:\WINDOWS\System32\RPCRT4.dll
C:\cygwin\bin\cygcrypto-0.9.7.dll
C:\cygwin\bin\cygssl-0.9.7.dll
Error: could not find cygperl5_8_2.dll

But I have the cygperl5_8_5.dll in the '/lib/' directory so...
What can I do ?