Well, there’s Nigeria to confuse things. It’s a former British colony and is pronounced “nigh-jeer-ee-ah”. But Niger was a former French colony and as such is pronounced more in the French manner: “nee-zhair”. The pronunciations didn’t make any sense to me until I learned about their history.
Up to the age of 18, I thought that you pronounced “epitome” as “ep-eh-tome”, until I actually used it in a sentence and was mocked thoroughly by a friend. Over 10 years later, and he still won’t let me live it down.
So. Embarassing.
ETA: At least it looks like I’m not alone. Phew.
I think in both of these cases, the older pronunciations you are familiar with are perfectly acceptable Anglicizations.
First time I came across “ethereal,” I had to look it up to find its meaning. Unfortunately, I didn’t look at the pronunciation. Of course, when I pulled it out to impress someone I was talking to about a book, I pronounced it eth-uh-real. The person I was trying to impress corrected me.
“Ignologe” actually sounds like the opposite of “knowledge.” 
If you ever say it wrong, just claim you’re doing a Jimmy Durante impression. He said it that way!
A couple years back, I learned that brassiere and brazier are not homophones. Led to some good burning bra jokes, though, so it’s all good.
Put me in on desultory, too.
For extra Dunce Cap points, I had to look up the meaning of the word–based on the prefix/root I would have thought the word meant ‘dismissive’.
It was well into college before I connected the spoken and written forms of ‘epitome,’ ‘segue,’ and ‘paradigm’.
A kind-of co-worker has, for the almost 11 years I’ve known her, recommended a particular online travel site, which is, apparently for her, Irish.
Travel O’City.
Being a perfect human being, I have never done this. Or at least, I can’t think of an instance right now.
But during a 6 week period between jobs, I took a really, REALLY crappy part time job, where I had this conversation with an esteemed co-worker.
Me: Hi! What do you need me to do?
Her: Huh?
Me: Well, I’m here, what should I do?
Her: Have you been assigned a pacific area?
Me: Excuse me?
Her: Well, you should get a pacific area, then you’ll go work there. Pacifically.
I thought she was going to send me to Seattle.
I didn’t say it out loud, but I was reading the other day and came across the word “rearms” course I read it as one syllable and thought “what the hell does that mean?” Had to look it up.
Well, that is the French pronunciation!
My roommate in college had a really cute boyfriend who was not the sharpest crayon in the box. We were discussing a mutual acquaintance one day and he said, “with her, it’s all a facade”, but he pronounced it fuh/kade/ee. We both looked at him and each other 
and then we got it. We roared.
He had other words, but I can’t recall them just now.
I totally dated that same guy. He once told me he was going home to watch “Acropolis Now.”
I think the first of many times this happened to me was when I was in grade school and my mother and I were shopping for a table cloth or some such thing. I proposed that we buy a “vinn-yl” tablecloth. Oops, it’s actually “vine-yl.”
The most recent I can think of was accenting the wrong syllable in “integral.” I thought it was pronounced “in-TEH-gral.”
My grandmother always told the story of the adults around her laughing their heads off when, as a young child, she announced that she hurt her arm and she was in “a-GOAN-ee.”
You’re not the only one–newscasters and other public speakers do this all the time.
On a less public scale, I had the final line in either an act or the whole play “The Importance of Being Earnest” and exclaimed “IN-famous!” (Luckily it was just in front of my family as we were running through it in preparation for seeing it.)
To this day, when I read the word “annihilate”, in my head I hear “ann uh hill ee yate.”
I realized “annihilate” is the word it is probably sometime in college.
It was funny, because I thought there were these two words meaning the same thing, one spelled “annihilate” and pronounced “annuhhilleeyate,” and the other pronounced the way annihilate is actually pronounced, and it never occured to me to wonder just exactly how you spell the latter word.
-FrL-
What exactly is the mistake? Webster’s has both ‘IN-teh-gral’ and ‘in-TEH-gral’ listed as valid, the former used primarily in the mathematics sense.
I’ve been guilty of “aw-ry”, “miss-happen”, and “mischie-vi-ous” too. My pronunciation of mischievous seems to be a regional thing (WI), because the only people I hear saying it the “correct” way are teachers from out of state, audiobooks, etc. I also feel rather lucky that I haven’t had the opportunity to embarrass myself over “desultory” before today.
The other thing that this thread reminded me of is chemistry. Not a week ago my organic chemistry professors assured us that “amide” could be “a-MID”, “a-MIDE”, “AY-mid”, “AM-id”, etc., just as long as you say it with confidence!