[Linraen]

Judging from my experience, it's possible (though by no means common) to have something like a short, one-handed glaive, and a shield.

The other, very real, option, is the one proposed by Corinthian, where you strap a buckler to your off hand. It's effective, but it can't be anything larger than a buckler (so if it's larger in game, it shouldn't be there).

However, in the case of game units (not the large ones that beat you up with two or more human-sized great mauls, anyway) it's either a programming/modding glitch or a case of confused definitions, I think.

Upd. to clear up the 'one-handed glaive' thing - considering how a glaive is just a spear with a wierd head, and how spears have been known across the agest to be able to both cut and thrust, AND have two- and one-handed variations, I guess it is possible.