Uncertainty for several hours Monday over the whereabouts of Irish singer Sinead O'Connor — who was found safe by Chicago-area police after a call saying she hadn't been seen since leaving for a bicycle ride Sunday — was only the latest episode involving the talented but troubled musician.

After scoring an international hit with her rendition of Prince's ballad, "Nothing Compares 2 U," O'Connor has been known as much for her fierce and expressive voice as for her blunt criticism of the Catholic Church and other institutions. O'Connor said she was diagnosed with bipolar disorder more than a decade ago and has spoken publicly of her mental health problems.

A brief look at some of her most-public disputes:

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ARSENIO HALL ALLEGATIONS

Comedian Arsenio Hall filed a libel lawsuit this month in Los Angeles against O'Connor over a Facebook post in which the singer accused him of furnishing Prince with drugs. The lawsuit said O'Connor wrote a Facebook post that stated investigators looking into the supplier of drugs used by Prince, who died in April, should question Hall. She also accused him of drugging her.

The comedian's lawsuit calls her accusations fabricated lies and states that O'Connor barely knew Prince. The lawsuit seeks more than $5 million in damages but any award would be decided by a jury.

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FACEBOOK MESSAGES

In November, the singer posted a message on Facebook saying she had taken an overdose at a hotel somewhere in Ireland. Irish police later said she had been found safe. The next month, O'Connor posted on Facebook that she had been detained in a hospital for mental health evaluation. O'Connor has been married four times and has four children, and she has posted online about ongoing disputes with her family over custody.

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MILEY CYRUS ARGUMENT

The Irish chanteuse warned the younger singer in an open letter in 2013 to avoid being sexually exploited by the music industry after Cyrus released her "Wrecking Ball" video, in which she appears nude and licking a sledgehammer. Cyrus responded on Twitter by mentioning O'Connor's struggles with bipolar disorder and compared her to troubled actress Amanda Bynes.

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SATURDAY NIGHT LIVE

O'Connor's most-famous protest of the Catholic Church came in 1992 when she appeared on "Saturday Night Live," singing "War" by the late Bob Marley. After her performance she tore up a photo of Pope John Paul II, saying "Fight the real enemy." Many viewers and church members expressed outrage and weeks later she was booed off the stage at Madison Square Garden during an event honoring Bob Dylan. This protest was years ahead of the child sex abuse scandal involving priests that would rock the Catholic Church.