I frequently hear people being interviewed on TV (especially reality shows) misusing prepositions, substituting incorrect ones in place of correct ones. Is there a name for this phenomenon?
Unfortunately, I don’t have an example off the top of my head.
Thanks,
Rob
A grammatical error? That’s what I would go with.
Do keep in mind though that prepositions are tricky little things. Their meaning is not quite as solid as people tend to expect them to be. So, it is possible that they’re not really using them wrong as much as they are using them differently from how you would.
You mean differently than how you would? 
Different from and different than are both correct. Some grammar Nazis like to point out that things differ from each other, they don’t differ than each other, but “different than” has been common usage for centuries.
Also, be aware that some varieties of English use prepositions in nonstandard ways, especially when they’re part of a verb phrase. For example, “throw out” in Malaysian English is merely “throw” – my Malaysia-born wife often asks me to “throw that piece of trash,” and I’m always tempted to fling it across the room.
What about “different to?”
d&r
Mostly British usage, so it tends to sound a bit odd to American ears, but also been around for ages and perfectly comulent.
I always say prepositions are like the neckties of grammar. It’s not particularly important which one you choose, as long as you have one. There are noticeable differences between languages in which preposition is “proper.” Germans go with the bus rather than on the bus or by bus, and even different strains of English have different usages.
Mr. Downtown, I love your necktie analogy, and agree with your point – but only as it applies to prepositions when they’re used to start a prepositional phrase. In Germanic languages, they’re also used to combine with verbs to change the meaning of the verb (sometimes subtly, sometimes greatly) – and in those instances, they’re not usually so interchangeable.
Not to mention the British “different to”. The idea that there is a fixed Platonic English is nonsense.
Which is why people only interchange the ones that don’t make a difference.
In common language you would see “I’m going to the store” and never “I’m going than the store” or “I’m going between the store.” “I’m standing in line” and “I’m standing on line” are both common, at least in some regions, because they both convey the same mental picture.
BTW, RadicalPi, this is a usage matter. Definitely not a grammatical error.