Windows7 and user-defined procedure

Hello!
I have user-defined procedure (C procedure) realised in dll ('c_some_text_dll'). It is called in the following way:

1. CREATE OR REPLACE FUNCTION "app_text" () RETURNS text AS
'$libdir/c_some_text_dll', 'getTextValueFromApplication'
LANGUAGE 'c' VOLATILE RETURNS NULL ON NULL INPUT SECURITY INVOKER;

2. CREATE TABLE "log" (
"id" SERIAL,
"value" TEXT DEFAULT app_text() NOT NULL
)

So when called from my application some stored procedure containing 'INSERT INTO log...' there was the result of 'app_text()' in the field 'value'.

It works in XP and Win2000. I'm trying to test in Windows 7 now and get an error when inserting data in table 'log': "Could not open relation base\16123\16222: No such file or directory".
The file '16222' exists and represents the table 'log' itself. All the imaginable rights for files and directories are set - as it seems to me.
One more detail - if I call this procedure from some other client application, f.e., psql (SELECT * FROM app_text()), before this INSERT - it begins to work in my application too.

Are there any ideas? I'll appreciate any help.

Thanks, Marina.