modem-man locks serial port/modem - /dev/ttyS0 locked or busy

i try to setup efax for use with an external serial modem to receive and send faxes.
since the pc has no onboard serial port i installed a serial controller card which is recognized and works

lspci says: .... 00:0e.0 Serial controller: NetMos Technology PCI 9835 Multi-I/O Controller (rev 01)

the modem ist found as well by wvdialconf: .... Found a modem on /dev/ttyS0.

but when trying to activate efax to listen on this port, it says: efax-0.9a: 19:38:43 Warnung: /dev/ttyS0 locked or busy - waiting

when looking what else is observing/using this port i find:

lsof | grep ttyS0
lsof: WARNING: can't stat() fuse.gvfs-fuse-daemon file system /home/chris/.gvfs
      Output information may be incomplete.
modem-man 880 root 18u CHR 4,64 0t0 1377 /dev/ttyS0

so i think something called modem man uses this port, but the strange thing is that a lockfile appears only in the /var/lock directory when i try to activate efax to be in the listen mode, and disappears after deactivating this.

the system used is ubuntu karmic 9.10 i386.

any help would be highly appreciated.