Same behavior with file-open:

CHICKEN
(c) 2008-2014, The Chicken Team
(c) 2000-2007, Felix L. Winkelmann
Version 4.9.1 (rev a3c7a5a)
windows-mingw32-x86 [ manyargs dload ptables ]
compiled 2014-05-04 on Cairo (MINGW32_NT-6.1)

#;1> (use posix)
; loading C:/MinGW//lib/chicken/7/posix.import.so ...
; loading library posix ...
#;2> (define fd (file-open "lobby.css" open/read))
#;3> fd
3
#;4> (define r (file-read fd 95))
#;5> r
("(use awful)\n\n(enable-sxml #t)\n\n(define-page (main-page-path)\n  (lambda ()
\n    \"Hello thero ther" 89)

However, if we add the binary flag:

CHICKEN
(c) 2008-2014, The Chicken Team
(c) 2000-2007, Felix L. Winkelmann
Version 4.9.1 (rev a3c7a5a)
windows-mingw32-x86 [ manyargs dload ptables ]
compiled 2014-05-04 on Cairo (MINGW32_NT-6.1)

#;1> (use posix)
; loading C:/MinGW//lib/chicken/7/posix.import.so ...
; loading library posix ...
#;2> (define fd (file-open "lobby.css" (+ open/read open/binary)))
#;3> fd
3
#;4> (define r (file-read fd 95))
#;5> r
("(use awful)\r\n\r\n(enable-sxml #t)\r\n\r\n(define-page (main-page-path)\r\n
(lambda ()\r\n    \"Hello ther" 95)