What version of lirc are you using?
This sounds like an old problem that has been fixed in the meantime. Try the CVS version.
When i do modprobe lirc_serial, i don't get any messages, but in dmesg i'm getting this:
kobject_add failed for lirc_serial.0 with -EEXIST, don't try to register things with the same name in the same directory.
[<f939b032>] init_module+0x32/0x2ac [lirc_serial]
[<f9281783>] journal_stop+0x193/0x1f0 [jbd]
irw doesn't work, it just exits and stops lircd.
i can see a /dev/lircd device, but nothing happens if i try to irrecord from it.
i'm using a homebrew receiver build as specified on lirc's webpage.