The Holux 245 is not yet fully supported. It will be fully supported once GPSBabel 1.3.7 becomes available.
GPSBabel 1.3.7 is currently available as a beta release. The m241 format should support the Holux 245 in that version.
The next question is to see which USB chipset is used by this device. This determines whether an additional USB driver is needed. The USB driver in turn determines under which name the device will be available.
I see you are using SLAB_USBtoUART. Are you using the SiLabs driver?
Houdah Software s.à r.l.