Problem opening a file in RTC

Hello:
It's happening something strange, I tell:
I've a codeunit which open a file and read that file and with that information create new records. But if i call that codeunit from the menusuite there isn't any problem but if a call that codeunit from OnOpenPage of one Page, it's going wrong, it can not open the file, fail when try open the file.

SetupSales.GET;
SetupSales.TESTFIELD(File);

IF NOT FicheroCentralita.OPEN(SetupSales.File) THEN BEGIN
ERROR(text001);
END;
.
.
.

Did i do something wrong??