I'm having a similar problem as well. In my case, it's a Hart Guisarme +1. I've checked spelling, capitalization, quotes, etc (including some obviously incorrect permutations). The /equip command doesn't work in or out of macro for this particular item, and I haven't noticed anything else in my inventory with this problem. If it matters, the spear is melded, but I didn't check to see if the /equip worked pre-melding (and can't really afford to buy another to test it right now).