Hi, I had this same issue with a Class 10 SanDisk Ultra 32GB microSD card, I bought it on October 2012 and used it happily in my Samsung Galaxy Note until February 2013 when I started facing this same problem, repeated messages that I had extracted the card until now when it is completely unreadable by either phone or computer.
I called SanDisk today and they said they would ship a replacement card, and denied that this is a specific problem with this card, said that millions of people use SanDisk cards successfully and only those who have problems write in forums for certain problems. Now I must take a picture of the card and send it to them, then I must destroy the card and they ship a replacement.
I hope this is not a general Class 10 problem… your explanation makes sense except for one point: why people (myself included) get to use the card happily for 3-4 months (approx) until it starts having problems? I had absolutely no problems before the time when I started getting the “card removed” messages. I don’t know about WP7, my experience is with Android 4.0.4 in my Galaxy Note 1 phone. I hope the replacement works.
Best and thanks for the info.