So I bought myself a tub of grease and the appropriately sized spanner in order that I might take out the BB on my bike (197X Motobecane Mirage), clean up all the old nasty grease, grime, and whatnot, and put some nice fresh grease in. But for the life of me, I can't get it open. The lock ring won't budge in either direction. I haven't tried a hammer or anything, just my arms.

Is there some step I'm missing, or is the blasted thing just seized?