http://bugs.winehq.org/show_bug.cgi?id=7526
--- Comment #16 from Bernie Innocenti bernie@codewiz.org 2009-06-10 15:59:12 --- It's most probably a timing-sensitve race condition of some kind, because slowing down wine -- for example, by enabling tracing -- made the testcase work normally.
I'm studying serial.c looking for clues.