Silicon oxide is a solid SiO2 other wise known as glass, and quartz to name a few minerals based on it. Why did you think it was a liquid, maybe I can find an explanation.
Hamish
Quartz are in fact Silicon DIOXIDE SiO2, Silicon Oxide or to give it its proper name Silicon Monoxide SiO, however is also solid with a melting point of 1702 degsC and a boiling point of 1880degsC its appearance is an odourless black powder, so I would suggest that unless you live slightly closer to the surface of the Sun than the rest of Earth's inhabitants you may be confusing it with something else.
Moog, as you said the correct name for SiO is silicon monoxide.
In general referance to XYZ oxide is a referance to the most common form (silicon dioxide in this case). It would be unlikely that someone who wants to know about common phases of silicon oxides would have access to SiO.
Uppon thinking about the question a little more, perhaps aikkian is thinking of a colloidal suspention of SiO2 in water (I have seen this for sale in the pharmacy) This would appear as a liquid but it is actually made up of SiO2 (silicon oxide) particles suspended in water. Hope this helps,