This is one of the more annoying problems I run across: leaf-tip burn. Some plants seem especially susceptible to it, including the spider plants I like so much and anything with longer leaves.
There are a number of conditions that cause leaf-tip burn, including using tainted water, overfeeding, and erratic watering habits. In my case, I suspect it's usually caused by my city's tap water (because of course, my watering and feeding habits are impeccable!). Nevertheless, it's annoying because it's cosmetic, and if I ask one thing out of houseplants, it's this: look good.
Okay, actually, the first thing I'd ask is, "Don't die." Then it's look good. But still ... it's up there.
[Edit: If you're looking for solutions, click here